UBRARl 
tTATE  PLANT  BOAR* 

Technical  Series,  No.  18. 

U.  S.  DEPARTMENT   OE  AGRICULTURE. 

HTJIZJ^.J^XJ    OF"    EN'rOMlOLOG-Y. 

L.  0.   HOWARD,    Entomoiogist  and   Chief  of  Bureau. 


THE  ANATOMY  OF  THE  HONEY  BEE. 


R.  E.  SNODGRASS, 

Agent  and  Expert. 


Issued  May  28,  1910. 


SB 


WASHINGTON: 

GOVERNMENT    PRINTING    OPPIOB, 

1910. 


Technical  Series,  No.  18. 

U.  S.  DEPARTMENT   OE  AGRICULTURE. 

JBXJRK^TJ    OF-    H^N'T^OMlOr^OOY. 

L.  0.   HOWARD,   Entomologist  and   Chief  of  Bureau. 


THE  ANATOMY  OF  THE  HONEY  BEE. 


BY 


R.  E.  SNODGRASS, 

Agent  and  Expert. 


Issued  May  28,  1910. 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE, 

1910. 


BUREAU    OF    ENTOMOLOGY. 

L.  O.  Howard,  Entomologist  and  Chief  of  Bureau. 

C.  L.  Marlatt,  Assistant  Entomologist  and  Acting  Chief  in  Absence  of  Chief. 

R.  S.  Clifton,  Executive  Assistant. 
W.  F.  Tastet,  Chief  Clerk. 

F.  H.  Chittenden,  in  charge  of  truck  crop  and  stored  product  insect  inrcMtigations. 

A.  D.  Hopkins,  in  charge  of  forest  insect  investigations. 

W.  D.  Hunter,  in  charge  of  southern  field  crop  insect  investigations. 

F.  M.  Webster,  in  charge  of  cereal  and  forage  insect  investigations. 
A.  L.  Quaintance,  in  charge  of  deciduous  fruit  insect  investigations. 
E.  F.  Phillips,  in  charge  of  bee  culture. 

D.  M.  Rogers,  in  charge  of  preventing  spread  of  moths,  field  icork. 
RoLLA  P.  CuRRiE,  in  charge  of  editorial  loork. 

Mabel  Colcord,  librarian. 

Investigations  in  Bee  Culture. 
E.  F.  Phillips,  in  charge. 

G.  F.  White,  J.  A.  Nelson,  B.  N.  Gates,  R.  E.  Snodgrass,  A.  II.  McCray,  agents 
and  experts. 

Ellen  Dashiell,  preparator. 
Jessie    E.    Marks,    clerk. 
T.  B.  Symons,  eollahorator  for  Maryland. 
H.  A.  Surface,  collaborator  for  Pennsylvania. 
J.  C.  C.  Price,  collaborator  for  Virginia. 
2 


LETT1:R  OF  TRAXSMI'ITAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Entomology, 
Washirigfoiu  D.  C ..  Octoher  19,  1909. 
Sir:  I  have  the  honor  to  transmit  herewith  a  manuscript  entitled 
'•  The  Anatomy  of  the  Honey  Bee,"'  by  Mr.  E.  E.  Snodgrass,  agent 
and  expert,  of  this  Bureau.  It  embodies  the  results  of  detailed 
studies  made  by  Mr.  Snodgrass  and  should  prove  of  value  as  bring- 
ing to  the  bee  keeper  reliable  information  concerning  an  insect  of 
such  great  economic  importance,  and  also  as  furnishing  a  sound 
basis  in  devising  new  and  improved  practical  manipulations.  I 
recommend  its  publication  as  Technical  Series,  No.  18,  of  the  Bureau 
of  Entomology. 

Respectfully,  L.  O.  Howard, 

Entomologist  and  Chief  of  Bureau. 
Hon.  James  Wilson, 

Secretary  of  Agriculture. 

3 


Digitized  by  the  Internet  Archive 
in  2013 


http://archive.org/details/anatomyofhoneybeOOsnod 


COXTHNTS. 

Page. 

I .  Introduction 9 

II.  General  external  structure  of  insects 10 

III.  The  head  ojf  the  bee  and  its  appendages 26 

1.  The  structure  of  the  head 26 

2.  The  antennae  and  their  sense  organs 32 

3.  The  mandibles  and  their  glands 39 

4 .  The  proboscis 43 

5.  The  epiphar\Tix 51 

IV.  The  thorax  and  its  appendages 53 

1.  The  structure  of  the  thorax 53 

2.  The  wings  and  their  articulation 59 

3.  The  legs 66 

V.  The  abdomen,  wax  glands,  and  sting 69 

VI.  The  alimentary  canal  and  its  glands 84 

1.  The  general  physiology  of  digestion,  assimilation,  and  excretion.  84 

2.  The  salivary  glands 87 

3.  The  alimentary  canal 90 

VII.  The  circulatory  system 107 

V^III.  The  respiratory  system 112 

IX.  The  fat  body  and  the  oenocytes 119 

X.  The  nervous  system  and  the  eyes 122 

XI.  The  reproductive  system 130 

1 .  The  male  organs 132 

2.  The  female  organs 134 

Explanation  of  the  symbols  and  letters  used  on  the  illustrations 1^9 

Bibliography 148 

Index 151 

5 


LLUSTRATIOXS. 


Page. 

Fig.  1 .  Median  longitudinal  section  of  body  of  worker 8 

2.  Diagram  of  generalized  insect  embryo 12 

3.  Example  of  generalized  insect  mouth  parts 17 

4.  Diagram  of  generalized  thoracic  segment 19 

5.  Typical  insect  leg 21 

().  Diagram  of  generalized  insect  wing  and  its  articulation 22 

7.  Diagram  of  terminal  abdominal  segments  of  a  female  insect  and  early 

stage  in  development  of  gonapophyses 25 

8.  Example  of  a  swordlike  ovipositor 25 

9 .  Head  of  worker  bee 27 

10.  Heads  of  worker,  queen,  and  drone 29 

11.  Median  longitudinal  sections  of  heads  of  worker  and  drone 30 

12.  Antennal  hairs  and  sense  organs 30 

13.  Mandibles  of  worker  and  drone 40 

14.  Internal  mandibular  gland  of  worker 4'i 

15.  Mouth  parts  of  worker 43 

10.  Median  section  through  distal  half  of  mentum  and  base  of  ligula  of 

worker 50 

17.  Epipharynx  and  labrum  of  worker 51 

18.  Sense  organs  of  epii)harynx 52 

19.  Median  longitudinal  section  of  head  of  worker 52 

20.  Dorsal  view  of  ventral  walls  of  body  of  worker 53 

21 .  Thorax  of  worker 54 

22.  Lateral  view  of  mesotergum  of  worker 50 

23.  Thoracic  terga  of  worker 57 

24.  U})per  j^art  of  left  mesopleurum  of  worker 58 

25.  Wings  of  Ilymenoptera - CO 

20.  Basal  elements  of  wings  of  Hymenoptera 01 

27.  Median  section  through  thorax  of  drone 04 

28.  Internal  view  of  right  pleurum  of  mesothorax  of  drone 65 

29.  Legs  of  worker,  queen,  and  drone 07 

30.  Claws  and  (un])odium  of  foot  of  worker 08 

31.  Tarsal  claws  of  worker,  queen,  and  drone 09 

32.  Lateral  view  of  abdomen  of  worker 70 

33.  Ventral  view  of  abdomen  of  worker 70 

34.  Dorsal  view  of  abdominal  sterna  of  drone 70 

35.  Sixth  abdominal  sternum  of  worker,  queen,  and  drone 7'J 

36.  Semidiagrammatic  view  of  left  side  of  sting  of  worker 75 

37.  Ventral  view  of  sting  of  worker 70 

38.  Section  of  small  ])iece  of  wall  of  poison  sac 79 

39.  Sections  of  alkaline  gland  of  Mling 79 

40.  Details  of  sting  of  worker -^l 

4 1 .  Tij)  of  abdomen  of  worker  with  left  side  removed S2 

6 


ILLUSTRATIONS.  7 

Page. 

Fig  .  42.  Alimentary  canal  of  worker 85 

43.  Details  of  pharyngeal  and  salivary  glands 88 

44.  Honey  stomach  of  worker,  queen,  and  drone U[ 

45.  Longitudinal  section  of  honey  stomach  and  proventriculun  of  (jueen  .  97 
40.  Histological  details  of  alimentary  canal  of  worker 103 

47.  Dorsal  diaphragm  of  drone,  from  one  segment 108 

48.  Small  part  of  dorsal  diaphragm  of  drone 110 

49.  Pericardial  chamber  of  one  segment  in  worker Ill 

50.  Tracheal  system  of  worker 113 

51.  Tracheal  system  of  worker 117 

52.  Nervous  system  of  worker 123 

53.  Brain  and  sub  oesophageal  ganglion  of  worker 125 

54.  Horizontal  section  of  compound  eye  and  optic  lobe  of  worker 127 

55.  Histological  details  of  compound  eye  of  worker 128 

bd.  Reproductive  organs  of  drone 133 

57.  Reproductive  organ  and  eting  of  queen 135 


THE  ANATOMY  OF  iHE  HONEY  BEE. 


I.    INTRODUCTION. 

The  anatomy  of  tlie  hone}^  bee  has  been  for  years  a  snbject  of  much 
interest  to  those  engaged  in  bee  keeping  both  for  pleasure  and  for 
profit.  This  interest  is  due  not  only  to  a  laudable  curiosity  to  know 
more  of  the  bee,  but  to  the  necessity  of  such  information  in  order 
to  understand  fully  what  takes  place  in  the  colony.  All  practical 
manipulations  of  bees  must  depend  on  an  understanding  of  the  be- 
havior and  physiology  of  bees  under  normal  and  abnormal  circum- 
stances, and  those  bee  keepers  who  have  advanced  bee  keeping  most 
by  devising  better  manipulations  are  those,  in  general,  who  know 
most  of  bee  activity.  In  turn,  a  knowledge  of  bee  activity  must  rest 
largely  on  a  knowledge  of  the  structure  of  the  adult  bee. 

Studies  on  the  anatomy  of  the  bee  have  not  been  lacking,  for 
many  good  workers  have  taken  up  this  subject  for  investigation. 
The  popular  demand  for  such  information,  however,  has  induced 
untrained  men  to  write  on  the  subject,  and  most  accounts  of  bee 
anatomy  contain  numerous  errors.  This  is  probably  to  a  gTeater 
extent  true  of  the  anatomy  of  the  bee  than  of  that  of  any  other 
insect.  Frequently  the  illustrations  used  by  men  not  trained  in 
anatomical  work  are  more  artistic  than  those  usually  found  in  papers 
on  insect  anatomy,  and  they  consequently  bear  the  superficial  marks 
of  careful  work,  but  too  often  it  is  found  that  the  details  are  in- 
accurate. It  has  therefore  seemed  the  right  time  for  a  new  presenta- 
tion of  this  subject  based  on  careful  work. 

The  drawings  given  in  the  present  paper  are  original,  with  the 
exception  of  figures  1-2.  54.  and  55,  and  have  been  prepared  with' 
a  thorough  realization  of  the  need  of  more  accurate  illustrations  of 
the  organs  of  the  bee,  especially  of  the  internal  organs.  Mistakes 
will  possibly  be  found,  but  the  reader  may  be  assured  that  all  the 
parts  drawn  were  seen.  Most  of  the  dissections,  moreover,  Avere 
verified  by  Dr.  E.  F.  Phillips  and  Dr.  J.  A.  Xelson.  of  this  Bureau, 
before  the  drawings  were  made  from  them.  An  explanation  of  the 
abbreviations  and  lettering  is  given  on  pages  139-147. 

It  is  hoped  that  the  work  will  furnish  the  interested  bee  keeper 
with  better  information  on  the  anatomy  of  the  bee  than  has  hereto- 
fore been  offered  to  him,  that  it  may  provide  a  foundation  for  more 
detailed  work  in  anatomy  and  histology,  and,  finally,  that  it  will  be 

9 


10  THE  AXATOMY  OF  THE  HOXEY  BEE. 

of  service  to  future  students  of  the  embryology  and  physiology  of 
the  bee.  With  this  last  object  in  view  the  writer  has  tried  to  sum 
up  under  each  heading  the  little  that  is  at  present  known  of  insect 
physiology  in  order  to  bring  out  more  clearly  what  needs  to  be  done 
in  this  subject. 

II.    GENERAL   EXTERNAL   STRUCTURE   OF   INSECTS. 

AMien  we  think  of  an  animal,  whether  a  bee,  fish,  or  dog,  we  uncon- 
sciously assume  that  it  possesses  organs  which  perform  the  same  vital 
functions  that  we  are  acquainted  with  in  ourselves.  We  know,  for 
example,  that  an  insect  eats  and  that  it  dies  when  starved ;  we  realize 
therefore  that  it  eats  to  maintain  life,  and  we  assume  that  this  involves 
the  possession  of  organs  of  digestion.  AYe  know  that  most  insects  see, 
smell,  and  perform  coordinated  actions,  and  we  recognize,  therefore, 
that  they  must  have  a  nervous  system.  Their  movements  indicate  to 
us  that  they  possess  muscles.  These  assumptions,  moreover,  are  en- 
tirely correct,  for  it  seems  that  nature  has  only  one  way  of  producing 
and  maintaining  living  beings.  No  matter  how  dissimilar  two 
animals  may  be  in  shape  or  even  in  fundamental  constitution,  their 
life  iDrocesses,  nevertheless,  are  essentially  identical.  Corresponding 
organs  may  not  be  the  same  in  appearance  or  action  but  they  accom- 
plish the  same  ends.  The  jaws  may  work  up  and  down  or  they  may 
work  sidewise,  but  in  either  case  they  tear,  crush,  or  chew  the  food 
before  it  is  swallowed.  The  stomach  may  be  of  very  diiferent  shape 
in  two  animals,  but  in  each  it  changes  the  raw  food  into  a  soluble  and 
an  assimilable  condition.  The  blood  may  be  red  or  colorless,  con- 
tained in  tubes  or  not,  but  it  always  serves  to  distribute  the  prepared 
food  which  diiiuses  into  it  from  the  alimentary  canal.  The  situa- 
tion of  the  central  nervous  system  and  the  arrangement  of  its  parts 
may  be  absohitely  unlike  in  two  organisms,  but  it  reguhites  the  func- 
tions of  the  organs  and  coordinates  the  actions  of  the  muscles  just 
the  same. 

Hence,  in  studying  the  honey  bee  we  shall  find,  as  we  naturally 
expect  to  find,  that  it  possesses  mouth  organs  for  taking  up  raw  food, 
an  alimentary  canal  to  digest  it,  salivary  glands  to  furnish  a  digestive 
liquid,  a  contractile  heart  to  keep  the  blood  in  circulation,  a  respira- 
tory system  to  furnish  fresh  oxygen  and  carry  oil'  waste  gases,  ex- 
cretory organs  for  eliminating  waste  substances  from  the  blood,  a 
nervous  systcMu  to  regulate  and  control  all  the  other  parts,  and,  finally, 
organs  to  pioducc  the  reproductive  elements  from  which  new  indi- 
viduals are  formed  to  take  the  i)laces  of  those  that  die. 

Tjie  study  of  anatomy  or  the  structure  of  the  oi'gans  themselves 
is  inseparably  connected  with  a  study  of  physiology  or  the  life 
functions  of  the  animal.  While  physiology  is  a  most  interesting 
and  important  subject,  and,  indeed,  in  one  sense  might  be  said  to  Ue 


GENERAL   EXTERNAL    STRUC^TURE    OF    INSECTS.  11 

the  object  of  all  aiiatoniical  research,  yet  the  mere  study  of  the 
structure  of  the  ()r<i:ans  alone,  their  wonderful  mechanical  adaj)ta- 
tions,  and  their  modifications  in  different  animals  forms  a  most  fasci- 
nating field  in  itself,  and  besides  this  it  gives  us  an  insight  into  the 
blood  relationship's  and  degrees  of  kinship  existing  between  the 
multitudes  of  animal  forms  found  in  nature.  In  the  study  of  com- 
parative anatomy  we  are  constantly  surprised  to  find  that  structures 
in  different  animals  which  at  first  sight  appear  to  be  entirely  differ- 
ent are  really  the  same  organs  which  have  been  simply  changed  in 
a  superficial  way  to  serve  some  new  purpose.  For  example,  the 
front  wing  of  a  bee  and  the  hard  shell-like  wing  cover  of  a  beetle  are 
fundamentally  the  same  thing,  both  being  front  wings — that  of  the 
beetle  being  hardened  to  serve  as  a  protection  to  the  hind  \\mg. 
Again,  the  ovii^ositor  of  a  katydid  and  the  sting  of  a  bee  are  identical 
in  their  fundamental  structure,  differing  in  details  simply  because 
they  are  used  for  different  purposes.  Hence,  in  the  study  of  anat- 
om}^  we  must  always  be  alert  to  discover  what  any  special  part  cor- 
responds with  in  related  species.  In  order  to  do  this,  however,  it 
is  often  necessary  to  know  the  development  of  an  organ  in  the 
embryo  or  in  the  young  after  birth  or  after  hatching,  for  many 
complex  parts  in  the  adult  have  very  simple  beginnings  in  an  imma- 
ture stage. 

Thus  it  becomes  evident  that  the  structural  study  of  even  one 
organism  soon  involves  us  in  the  subjects  of  anatomy,  physiolog\\ 
and  embryology,  and.  if  we  add  to  this  a  study  of  its  senses,  its 
behavior,  and  its  place  in  nature,  the  field  enlarges  without  limit. 
The  student  of  the  honey  bee  realizes  that  a  lifetime  might  be  spent 
in  exploiting  this  one  small  insect. 

The  differences  between  animals  are  much  greater  on  the  outside 
than  on  the  inside.  In  the  descriptions  of  the  organs  of  the  honey  bee 
anyone  will  know  what  is  meant  by  the  '*  alimentary  canal,''  the 
••  nervous  system,"  or  the  "  respiratory  system,"  but  the  external 
parts  are  so  different  from  those  of  animals  with  which  we  are  more 
familiarly  acquainted  that  no  general  reader  could  be  expected  to 
know  what  is  meant  by  the  names  applied.  Moreover,  the  bee  and  its 
allies  are  so  modified  externally  in  many  ways  that,  at  first  sight, 
their  parts  look  very  different  even  from  those  of  other  insects. 
Hence,  we  shall  give  a  preliminary  account  of  the  external  structure 
of  insects  in  general,  for  it  is  hoped  that  the  reader  will  then  more 
easily  understand  the  special  structure  of  the  honey  bee.  and  that  the 
application  of  the  terms  used  will  appear  more  reasonable  to  him. 

Since  all  animals  originate  in  an  egg,  the  change  into  the  adult 
involves  two  different  processes:  One  is  growth,  which  implies 
mereh^  an  increase  in  size,  the  addition  of  material  to  material:  the 
other  is  development,  which  means  change  in  shape  and  the  produc- 


12 


THE    ANATOMY    OF    THE    HONEY    BEE. 


tion  of  a  form  Avitli  complex  organs  from  the  simple  protoplasmic 
mass  of  the  egg.  The  part  of  deAxlopment  that  takes  place  in  the 
eggshell  is  known  as  emhryonic  development;  that  which  takes  place 
subsequent  to  hatching  is  known  as  postembryonic  decelopment.  In 
insects  there  are  often  two  stages  in  the  postembryonic  development, 
an  active  one  called  the  larval  stage  and  an  inactive  one  called  the 
pupal  stage.  During  the  first  of  these  the  young  insect  is  termed  a 
larva;  during  the  second,  a  pupa.  When  there  is  no  resting  stage  the 
immature  creature  is  often  called  a  nymph.  The  final  and  fully  de- 
veloped form  is  an  adult^  or  imago. 

Since  this  paper  is  to  deal  only  with  the  anatomy  of  the  adult,  the 
attractive  fields  of  embryonic  and  postembryonic  development  must 
be  passed  over,  except  for  a  few  statements  on 
fundamental  embryonic  structure,  a  knowledge 
of  which  is  necessary  to  a  proper  understanding 
of  the  adult  anatomy. 

When  the  embryo,  in  its  course  of  development, 
first  takes  on  a  form  suggestive  of  the  definitive 
insect,  it  consists  of  a  series  of  segments  called 
metameres,  or  somites^  and  shows  no  differentia- 
tion into  head,. thoracic,  and  abdominal  regions. 
Tjqjically,  each  segmewt  but  the  first  is  provided 
with  a  pair  of  latero- ventral  appendages^  hav- 
ing the  form  of  small  rounded  ])rotuberances. 
These  appendages  are  of  dilferent  sizes  and  take 
on  different  shapes  in  different  parts  of  the 
body,  for  some  of  them  are  destined  to  form  the 
antenna\  some  the  mouth  parts,  others  the  legs 
and  perhaps  the  cerci,  while  the  rest  of  them 
remain  very  small  and  finally  disappear.  What 
we  know  of  the  embryology  of  insects  is  based 
on  the  observations  of  a  number  of  men  who 
have  worked  mostly  on  the  development  of  dif- 
ferent species.  Their  observations  are  not  all 
alike,  but  this  is  probably  due  in  large  part  to  the  fact  that  the 
embryos  of  diff'erent  insects  are  not  all  alike.  Embryos  have  a  xcvy 
provoking  habit  of  skipping  over  or  omitting  little  and  yet  im- 
portant things  m  their  development,  bul  fortunately  ihey  do  not 
all  omit  the  same  tilings.  Therefore.  l)v  putting  together  all  the 
reliable  information  we  possess,  we  can  make  up  :in  idc^d  embryo 
which  would  be  typical  of  all  insects.  Such  a  generalized  embryo  is 
represented  diagrannnatically  by  figure  *J. 

The  first  six  or  seven  metameres  \ery  early  begin  to  unite  with 
one  another  and  continue  to  fnse  until  their  boi'ders  are  lost.  These 
consolidated  I'mbi-yonic  segments  form  the  head  of  the  adult  insect. 


Lm  ~  y 

^^    —  -^ 

V 

MthX 

'tt^ 

V-  I  Ant 
:{— 2Ant 

1 

Lin-H 

ml 

t-Md 

KM^ 

-2Mx 

Bo^ 

— iL 

m 

— 2L 
-3L 

i 

An- 

Fig.  2. — Diagram  of  a 
goneralized  insect  (>m- 
hryo,  showing  tlie  sej?- 
mcntation  of  the  head, 
thoracic,  and  alidom- 
inal  rc^'ions,  and  the 
s('',Mncntal  appendages. 


GENERAL    EXTERNAL    STRUCTURE    OF    INSECTS.  13 

Observers  differ  concern iiii^-  the  fate  of  the  seventh  segment,  but  it 
is  most  2)robable  that  a  part  of  it  fuses  Avi»th  the  sixth  segment,  thus 
taking  part  in  the  formation  of  the  head,  and  tliat  a  part  of  it  forms 
the  neck  or  some  of  the  neck  phites  of  the  a(hdt. 

The  appendages  of  these  first  seven  segments  form  the  antennae 
and  mouth  parts,  except  one  or  two  pairs  that  disappear  early  in 
embryonic  life.  It  is  not  certain  that  the  first  segment  ever  possesses 
appendages,  but  from  it  arise  the  large  compound  eyes  and  appar- 
ently also  the  upper  lip,  or  labrum  (Lm).  The  appendages  of  tlie 
second  segment  form  the  feelers,  or  antennne  {J Ant)  of  the  adult, 
those  of  the  third  (2 Ant)  disappear  in  insects,  but  they  correspond 
with  the  second  antenna?  of  shrimps  and  lobsters.  The  appendages 
of  the  fourth  segment  form  the  mandibles  (Md).  Those  of  the 
fifth  segment  (Slin),  when  present,  fuse  with  a  median  tonguelike 
lobe  {Lin)  of  the  following  segment,  and  the  three  constitute  the 
hypojDharynx,  or  lingua  of  the  adult.  The  next  pair  (IMx)  form  the 
maxillae,  w^hile  the  last  {2Mx)^  or  those  of  the  seventh  segment, 
coalesce  w4th  each  other  and  constitute  the  adult  labium,  or  lower  lip. 

The  bodies  of  the  head  metameres  fuse  so  completely  that  it  is 
impossible  to  say  positively  what  parts  of  the  adult  head  are  formed 
from  each.  The  last,  as  already  stated,  possibly  takes  part  in  the 
formation  of  both  the  head  and  the  neck.  Some  embryologists  at- 
tribute the  plates  wdiich  usually  occur  in  this  region  to  the  last  em- 
bryonic head  segment,  while  others  believe  they  come  from  the  next 
segment  following.  Sometimes  these  plates  are  so  well  developed 
that  they  appear  to  constitute  a  separate  segment  in  the  adult,  and 
this  has  been  called  the  microthorax.  If  this  name,  however,  is 
given  to  the  embryonic  segment  from  which  these  plates  are  said  to 
be  derived,  it  must  be  remembered  that  it  is  not  "  thoracic  "  at  all 
and  belongs  partly  to  the  head.  The  name  cervicum  has  been  ap- 
plied to  the  neck  region  with  greater  appropriateness  since  it  does 
not  imply  any  doubtful  affiliation  with  adjoining  regions.  What 
we  really  need,  however,  is  not  so  much  a  name  as  more  information 
concerning  the  development  of  the  rear  part  of  the  head  and  the 
neck  plates  in  different  insects. 

The  next  three  segments  remain  distinct  throughout  life  in  nearly 
all  insects,  but,  since  they  bear  the  legs  and  the  wings,  they  become 
highly  specialized  and  together  constitute  the  thorax.  The  indi- 
vidual seg-ments  are  designated  the  prothorax^  the  mesotlwrax^  and 
the  metathorax.  The  legs  are  formed  from  the  embryonic  ap- 
pendages (fig.  2,  7Z,  2L^  3L)  of  these  segments,  but  the  wings  are 
secondary  outgrowths  from  the  mesothorax  and  metathorax  and 
are,  hence,  not  appendages  in  the  strict  embryological  sense. 

The  remaining  segments,  nearly  always  10  in  number,  constitute 
the  abdomen.     The  appendages  of  these  segments,  except  possibly 


14  THE  ANATOMY  OF  THE  HONEY  BEE. 

those  of  the  tenth,  disappear  early  in  embryonic  life  in  all  insects, 
except  some  of  the  very  losvest  species,  in  which  they  are  said  to  form 
certain  small  appendages  of  the  abdominal  segments  in  the  adults. 

An  adult  insect  is  often  described  as  being  "  divided  ''  into  a  head,  a 
thorax,  and  an  abdomen,  but  this  is  not  true  in  most  cases.  While  all 
insects  consist  of  these  parts,  the  divisions  of  the  body  are  usually 
not  coincident  with  them.  The  prothorax  in  the  adult  is  separated 
from  the  head  by  the  neck  and  is  very  commonly  separated  from  the 
mesothorax  by  a  flexible  membranous  area.  On  the  other  hand,  the 
mesothorax  and  metathorax  are  almost  always  much  more  solidly  at- 
tached to  each  other,  while,  in  most  insects,  the  metathorax  is  solidly 
and  widely  joined  to  the  first  abdominal  segment,  though  in  the  flies 
these  latter  tAvo  segments  are  usually  separated  by  a  constriction.  In 
such  insects  as  ants,  wasps,  and  bees  a  slender,  necklike  peduncle 
occurs  between  the  first  and  second  segments  of  the  abdomen,  the 
first  being  fused  into  the  metathorax  so  that  it  appears  to  be  a  part 
of  the  thorax.  This  is  the  most  distinctive  character  of  the  order 
Hymenoptera.  to  which  these  insects  belong. 

The  body  wall  of  insects  is  hard  on  account  of  the  thick  layer  of 
chitin  which  exists  on  the  outer  side  of  the  true  skin.  Chitin  is  a  sub- 
stance similar  to  horn,  being  brittle,  though  tough  and  elastic.  It 
gives  form  and  rigidity  k)  the  body  and  affords  a  solid  attachment  for 
the  muscles  within,  since  insects  have  no  internal  framework  of  bones 
such  as  vertebrate  animals  have.  The  skin  between  the  segments  is 
soft  and  unchitinized  and  thus  forms  a  flexible  intersegmental  mem- 
brane which  is  often  ver}^  ample  and,  in  the  abdomen,  allows  each  seg- 
ment to  telescope  into  the  one  in  front  of  it. 

The  chitin  of  each  segment  is  not  continuous,  but  is  divided  into 
plates  called  sclentes.  The  most  important  of  these  are  a  ter-gum 
above  and  a  sternum  below,  but,  in  the  case  of  the  thorax,  these  two 
plates  are  separated  on  each  side  by  another  called  the  pleunim^  which 
lies  between  the  base  of  the  wing  and  the  base  of  the  leg.  Pleural 
plates  are  sometimes  present  also  on  the  abdominal  segments.  These 
principal  segmental  plates  are  usually  separated  by  membranous 
lines  or  spaces,  which  permit  of  more  or  less  motion  between  them. 
Such  lines  are  called  sutures  in  entomology,  though  strictly  this  term 
should  be  applied  only  to  the  lines  of  fusion  between  adjoining  parts. 

The  terga,  pleura,  and  sterna  of  each  segment  are  furthermore 
subdivided  into  smaller  sclerites,  which  may  be  (eruKHl  tergites^  ple^(- 
rites,  and  stcrnltes.  respectively.  The  sutures  between  them  are 
sometimes  membranous  also,  but  most  frequently  have  the  form  of 
impressed  lines  or  niurow  grooves.  In  such  cases  they  are  generally 
nothing  more  than  tlie  cxtei'ual  marks  of  ridges  developed  on  the 
inside  of  the  body  wall  to  strengthen  tiie  ])arts  oi"  to  give  attachinenr 
to  nmscles.     Since  these  sutui-es  nic  conspicuous  marks  on  {\\v  oulsi(k* 


GENERAL   EXTERNAL    STRUCTURE    OF    INSECTS.  15 

of  an  insect,  they  are  usually  re<2,ai(le(l  as  nioipholo^ically  impor- 
tant things  in  themselves,  representing  a  tendency  of  the  terguni,  i)leu- 
rum,  or  sternum  to  separate  into  smaller  plates  for  some  reason.  The 
truth  about  them  would  appear  to  be  just  the  opposite  in  most  cases — 
they  are  the  unavoidable  external  marks  of  an  internal  thickening 
and  strengthening  of  the  plates.  In  a  few  cases  they  may  be  the 
confluent  edges  of  separate  centers  of  chitinization.  Hence,  most  of 
the  sutural  lines  in  insects  appear  to  signify  a  bracing  or  solidifying 
of  the  body  wall  rather  than  a  division  of  it. 

Since  the  body  wall  of  insects  is  continuous  over  all  the  surface  it 
contains  no  articulations  of  the  sort  that  occur  between  the  bones  in 
the  skeleton  of  a  vertebrate.  Although  insects  and  their  allies  l)e- 
long  to  the  class  of  animals  known  as  the  Articulata,  yet  an  articu- 
late articulation  is  simply  a  flexibility — two  chitinous  ])arts  of  the 
exoskeleton  are  movable  upon  each  other  simply  by  the  intervention 
of  a  nonchitinized,  flexible,  membranous  part.  While  there  are  often 
special  ball-and-socket  joints  developed,  these  are  ahvays  produced 
on  the  outside  of  the  membranous  hinge  and  simply  control  or  limit 
the  movement  of  the  articulation. 

The  head  of  an  adult  insect  is  a  thin-walled  capsule  containing  the 
brain,  the  ventral  head  ganglion  of  the  nervous  system,  the  pharynx 
and  anterior  part  of  the  oesophagus,  the  tracheal  tubes,  and  the 
muscles  that  move  the  antennae  and  the  mouth  parts.  Its  shape  varies 
a  great  deal  in  different  insects,  being  oval,  globular,  elongate,  or 
triangular.  In  some  it  is  flattened  dorso-ventrally  so  that  the  face  is 
directed  upward  and  the  mouth  forward,  but  in  most,  including 
the  bee,  it  is  flattened  antero-posteriorly  so  that  the  face  looks  for- 
ward and  the  mouth  is  directed  ventrally.  In  a  few  it  is  turned  so 
that  the  face  is  ventral.  The  walls  of  the  head  are  usually  divided 
by  sutures  into  a  number  of  sclerites,  which  in  general  are  located 
and  named  as  follows:  The  movable  transverse  flap  forming  the 
upper  lip  is  the  labrum.  Above  it  is  a  sclerite  called  the  clypeus^ 
Avhich  is  a  part  of  the  solid  wall  of  the  head  and  carries  the  anterior 
articulations  of  the  mandibles.  The  clypeus  is  sometimes  divided 
transversely  into  an  anteclypeus  ("clypeus  anterior,"  "epistoma'") 
and  into  a  post-clypeus  ("clypeus  posterior").  Above  the  clypeus 
is  the  front,  a  plate  usually  occupying  the  upper  half  of  the  face 
between  the  compound  eyes  and  carrying  the  antennae.  The  top  of 
the  head  is  called  the  vertex,  but  does  not  constitute  a  separate  scle- 
rite. The  sides  of  the  head  below  the  compound  eyes  are  often  sepa- 
rated by  sutures  from  the  anterior  and  posterior  surfaces  and  are 
known  as  the  gence.  The  back  of  the  head  is  formed  by  the  occiput. 
which  surrounds  the  large  opening  or  foramen  niagnunri  that  leads 
from  the  cavity  of  the  head  into  that  of  the  neck.  The  parts  pos- 
terior to  the  gena?,  carrying  the  posterior  mandibular  articulations, 


16  THE  ANATOMY  OF  THE  HOXEY  BEE. 

are  sometimes  separated  from  both  the  occiput  and  the  genae  and  are 
known  as  the  postgenw.  In  a  few  insects,  especially  beetles,  one  or 
two  median  plates  occur  in  the  ventral  wall  of  the  head  posterior  to 
the  base  of  the  labiimi.  These  are  the  gidar  sclerites.  Finally,  small 
plates  are  sometimes  found  about  the  bases  of  the  antenna^  and  be- 
tAveen  the  bases  of  the  mandibles  and  the  geniT.  The  latter  have 
been  termed  the  trochantins  of  the  mandihles.  The  term  cpicran'nim 
is  often  used  to  include  all  the  immovable  parts  of  the  head,  but  is 
frequently  applied  only  to  the  dorsal  parts.  Most  of  these  sclerites 
preserve  a  pretty  definite  arrangement  in  the  different  orders,  and 
they  are  probably  homologous  throughout  the  entire  insect  series, 
though  they  are  in  some  cases  very  much  distorted  by  special  modi- 
fications and  are  often  in  part  or  wholly  obliterated  by  the  disap- 
pearance of  the  sutures.  Elmbryologists  are  coming  to  the  conclu- 
sion that  the  sclerites  of  the  head  have  no  relation  to  the  primitive 
segments.  The  latter  very  earty  consolidate  into  a  head  with  a  con- 
tinuous wall,  while  the  sutures  defining  the  sclerites  are  formed 
later.  Some  of  the  older  entomologists  were  led,  from  a  study  of 
the  sclerites,  to  suppose  that  the  head  consisted  of  a  number  of  seg- 
ments, but  it  has  been  shown  that  these  anatomical  segments  do  not 
correspond  with  the  embryonic  ones. 

The  appendages  growing  from  the  front  of  the  face  are  the 
antennae  (fig.  9A,  Ant)  or  "  feelers  "  and  consist  of  a  series  of  joints 
or  segments. 

At  the  lower  edge  of  the  face  is  the  front  lip  or  1  ah  nun  (fig.  9  A, 
Lm)^  behind  which  are  the  median  ep'i pharynx^  the  paired  mandihles 
{Md)  and  maxillce,  the  median  hypophart/nx.  and  the  lahium  or  under 
lip.  All  these  organs  together  constitute  what  are  known  as  the 
mouth  parts  or  tropin.  They  vary  greatly  in  shape  and  appearance 
in  different  insects  according  to  the  nature  of  the  food,  but  their 
typical  form  is  usually  taken  to  be  that  shown  by  the  lower  insects 
which  feed  on  solid  food  and  have  biting  mouth  parts.  Figure  3, 
representing  tlie  jaws  and  lips  of  the  connnon  bhu'k  cricket,  is  given 
as  an  example  of  generalized  insect  mouth  parts. 

The  labium  (fig.  9A.  Lni)  is  usually  a  simi)le  transverse  flap  in  front 
of  the  mouth,  being  developed,  as  already  shown,  from  a  similarly 
situated  lobe  on  the  first  segment  of  the  embryo  (fig.  "J.  Lm). 

The  epipharynx  (fig.  19,  h^phy)  is  a  soi't  of  dorsal  tongue,  and  is 
situated  on  the  membrane  leading  into  the  mouth  from  behind  the 
labrnm. 

The  mandibles  (figs.  3A;  9A,  Md)  are  tyi)ically  formed  for 
biting,  being  heavy  organs  situated  innnediately  behind  the  labrum 
and  working  sidewise  on  a  hinge  articidation  with  the  lu^ad.  Their 
cutting  edges  are  usually  notched  and  toothed,  though  smooth  in  the 
worker  bee. 


GENERAL   EXTERNAL   STRUCTURE    OF    INSECTS. 


17 


The  maxillae  (fi^-.  ^\  B  and  B)  are  coinplicated  appendages  in  tlieii- 
typical  form.  Each  consists  of  a  principal  piece  called  the  stipes  {Ht) , 
which  is  hinged  to  the  head  by  means  of  a  smaller  basal  piece,  th(5 
cardo  (Cd).  Terminally  the  stipes  bears  an  outer  lobe,  the  r/alea 
(Ga),  and  an  inner  lobe,  the  lacinia  (Lc).  On  the  outer  side,  at  the 
base  of  the  galea,  it  carries  a  jointed  appendage  called  the  maxillary 
palpus  {Pip). 

The  hypopharynx  (fig.  3  C  and  D,  Uphy)  is  a  median,  ventral, 
tonguelike  organ,  called  also  the  lingua^  situated  either  on  the  upper 
surface  of  the  labium  or  on  the  membrane  between  this  organ  and  the 
mouth.  It  is  de- 
veloped principally 
from  a  median  lobe 
of  the  head  pf  the 
embryo  behind  the 
mouth  (fig.  2,  Lin), 
but  some  entomol- 
ogists claim  that  it 
is  compounded  of 
this  lobe  and  two 
smaller  lateral  ones 
developed  from  the 
appendages  of  the 
fifth  embryonic 
head  segment  (fig. 
2,  Slin)^  the  super- 
linguce. 

The  labium  (fig. 
3  C  and  D)  consti- 
tutes the  under  lip 
of  the  adult,  but  it 
is  formed  from  the 
two  appendages  of 

the  seventh  segment  in  the  embryo,  which  fuse  with  each  other.  For 
this  reason  it  is  often  called  the  second  maxillae  It  consists  of  a  basal 
suhmentumfh  {Smt)  bearing  the  mentum  {Mt)^  which  in  turn  carries 
three  parts,  a  median  ligula  {Lg)  and  two  lateral  palpigers  {Pig). 
The  latter  support  the  labial  palpi  {Plp)^  while  the  ligula  bears  four 
terminal  lobes,  of  which  the  median  ones  are  called  the  glossm  {Gls) 
and  the  lateral  ones  the  paraglossm  {Pgl).  If  we  should  cut  the 
labium  into  two  parts  along  its  midline  we  should  see  that  even  in 
the  adult  stage  each  half  is  very  similar  to  one  maxilla.  The  only 
discrepancy  to  be  noticed  in  the  example  given  (fig.  3)  is  that  there 
22181— No.  18—10 2 


Fig.  3. — Example  of  generalized  insect  mouth  parts,  from 
common  black  cricket  (Gryllus  pennsylvanicus)  :  A,  man- 
dibles ;  B,  B,  maxillae,  ventral  view ;  C,  labium  or  second 
maxillse,  ventral  view :  D,  labium,  lateral  view. 


18  THE  ANATOMY  OF  THE  HOXEY  BEE. 

is  no  maxillary  palpiger.  but  many  insects  possess  a  corresponding 
part  in  the  maxilla,  frequently  distinguished  as  the  palfifer. 

The  neck  or  cervicum  is  usually  a  short  membranous  c^dinder  which 
allows  the  head  great  freedom  of  motion  upon  the  thorax.  In  nearly 
all  insects  its  lateral  walls  contain  several  small  plates,  the  cervical 
sclerites^  while,  in  many  of  the  lower  species,  dorsal,  ventral,  and 
lateral  sclerites  are  present  and  highly  developed.  As  already  stated, 
the  origin  of  these  plates  is  doubtful.  Some  entomologists  would 
derive  them  from  the  prothorax,  others  think  they  come  from  the 
last  head  segment,  while  still  others  think  that  they  represent  a 
separate  segment.  Only  pure  anatomists,  however,  entertain  this 
last  view  and  call  this  supposed  segment  the  "  microthorax,''  for 
embryologists  have  not  yet  reported  a  metamere  between  the  labial 
segment  and  the  prothoracic  segment.  Most  embryologists  who  have 
studied  the  subject  admit  that  some  of  the  cervical  sclerites  may  be 
formed  from  the  last  embryonic  head  somite  which  carries  the  labium 
and  probably  forms  a  part  of  the  back  of  the  head.  Therefore,  if 
it  is  desirable  to  retain  the  word  microthorax  as  a  name  for  a  true 
segment,  it  can  be  applied  only  to  this  labial  metamere.® 

The  thorax,  as  has  already  been  stated,  is  a  distinct  anatomical 
region  of  the  body  rather  than  a  "  division  "  of  tlie  body,  since  it  car- 
ries both  the  legs  and  the  wings  and  contains  the  large  muscles  for 
each.  Since  the  prothorax  does  not  possess  wings,  it  is  not  so  highly 
developed  otherwise  as  the  two  wing-bearing  segments,  and  is,  indeed, 
generally  reduced  in  some  ways,  some  of  its  parts  being  frequently 
rudimentary.  Therefore  we  shall  base  the  following  description  of 
a  typical  segment  on  the  structure  of  the  Aving-bearing  segments. 

A  typical  thoracic  segment,  then,  presents  four  surfaces,  as  does  also 
the  entire  body.  These  are  a  dorsuin  above,  a  roitcr  below,  and  a 
latus^  on  each  side.     From  these  names  we  have  the  terms  "dorsal," 

"  In  a  former  paper  on  the  thorax  of  insects  (Proc.  U.  S.  Nat.  Miis.,  XXXVI, 
1909,  i»i).  511-595)  the  writer  probably  drew  a  too  definite  conclusion  on  the 
subject  of  the  "microthorax."  The  orijiin  of  the  neck  sclerites  has  ])robahly 
never  yet  been  actually  observed.  Comstock  and  Kochi  (Amer.  Nat.,  XXX VI, 
1902,  pp.  13^5),  in  summarizing  the  sedimentation  of  the  head,  accredited 
the  j^ular  and  cervical  sclerites  to  the  labial  sejjment,  but  did  not  recognize  the 
latter  as  taking  part  in  the  formation  of  the  true  head  capsule.  Riley,  how- 
ever, in  his  study  of  the  development  of  the  head  of  a  cockroach  (Amer.  Nat., 
XXXV in,  1904,  i)p.  77T-.S10),  states  tbat  in  lilntta  the  labial  segnienl  does 
I'onii  a  part  <»f  the  back  of  tbe  head  and  that  the  posterior  anus  of  the 
leiitorium  are  <lerived  from  it.  Hiirner  (Zool.  Anz.,  XXVI,  IIMKJ,  pp.  290-;)15) 
and  C'rampton  (Proc.  Acad.  Nat.  Sci.  Phila.,  1909,  i)p.  .S-54)  believe  that  the 
cervical  sclerit<'s  are  derived  principally  from  the  prothoracic  segment.  The 
notion  tbat  they  coiistitut<'  a  sejiarate  segment,  the  "microthorax,"  equivalent 
to  the  iiiaxilliped  segment  of  the  centipedes,  has  been  elaborated  i>rincipal]y 
by  \'erhoeff  in   his  iiiiinci-ous  writings  on   the  (Miilopoda   and   Dermaptera. 

''The  writci-  intr(»(lMces  liiis  woi-d  licrc  Ix'cnusc  he  laiows  of  no  other  term 
applied   to  the  si<lc  of   the  segnM-nt    in   tills  sense. 


GENERAL   EXTERNAL   STRUCTURE    OF    INSECTS. 


19 


"  ventral,"  and  "  lateral."  The  chitinous  parts  of  the  dorsum  con- 
stitute the  tergum;  of  the  venter,  the  sternum;  and  of  the  latus,  the 
pleurum. 

The  tergum  of  the  wing-bearing  segments  usually  consists  of' 
two  plates — a  front  one  or  true  notum  (fig.  4,  N)  carrying 
the  wings,  and  a  posterior  one,  which  the  writer  has  termed  the 
postnotum  or  pseudonotuTn  {PN)^  having  no  connection  with  tlie 
wings.  The  first  is  often  more  or  less  distinctly  marked  into  three 
transverse  parts  called  the  prescutum  (Psc),  sciitiim  (Set),  and  sctt- 
tellimi  {Scl).  In  such  cases  the  exposed  part  of  the  postnotum  is 
called  the  postsciitellum  (Pscl).  From  either  the  anterior  or  the  pos- 
terior margin  of  the  tergum,  or  from 
both,  a  thin  transverse  plate  projects 
downward  into  the  interior  of  the 
thorax  for  the  attachment  of  muscles. 
These  plates  are  the  phragmas  {Aph 
and  Pph).  The  notum  supports  the 
wing  on  each  side  by  two  small  lobes, 
the  anterior  and  posterior  noted  loirig 
processes  {ANP  and  PNP).  Behind 
the  latter  is  the  attachment  of  the 
axillary  cord  (AxC)  or  basal  ligament 
of  the  wing.  A  large  V-shaped  ridge 
on  the  under  surface  of  the  notum  hav- 
ing its  apex  forward  is  the  "  entodor- 
sum."  (A  better  name  would  be 
entotergum.) 

The  pleurum  consists  principally  of 
tAvo  plates,  the  episternum  (fig.  4,  Eps) 
and  the  epimerum  (Epm)  l3ang  before 
and  behind  a  vertical  groove,  the  pleural  suture  {PS)^  which  extends 
from  the  pleural  coxal  process  (CxP)  below  to  the  pleurcd  loing 
process  {WP)  above.  The  pleural  suture  marks  the  position  of  a 
heavy  internal  ridge,  the  pleural  ridge  or  entopleurum.  The  epi- 
merum is  connected  with  the  postnotum  {PN)  behind  the  base  of  the 
Aving.  These  parts  occur  in  almost  all  insects.  In  some  of  the  lower 
ones  another  plate  is  present  in  front  of  the  episternum  which  may 
be  called  the  preepisternum  {Peps),^    Lying  along  the  upper  edge  of 


Fig.  4. — Diagram  of  generalized 
tlioracic  segment,  left  side. 


°  Objection  may  be  made  to  the  use  of  the  term  "  preepisternum "  on  the 
ground  that  it  combines  a  Latin  prefix  with  a  word  compounded  of  Greelv  ele- 
ments. The  same  may  be  urged  against  "  prephragma,"  "  postphragma,"  "  pre- 
I)araptera,"  and  "  postparaptera,"  words  introduced  by  the  present  writer  in  a 
former  paper  on  the  thorax  (Proc.  U.  S.  Nat.  Mus.,  XXXVI,  1909,  pp.  .511-595). 
However,  we  are  barred  from  mailing  up  equivalent  terms  with  the  Greek  pre- 
fixes pro  and  mcta  because  these  are  used  to  designate  the  first  and  the  third 


20  THE  ANATOMY  OF  THE  HOXEY  BEE. 

the  pleurum  and  associated  with  the  under  surface  of  the  wing  base 
are  several  small  plates  known  as  the  faraftera  (P).^  Two  lie  above 
the  episternum  in  front  of  the  pleural  wing  process  and  are  the 
episternal  paraptera  or  preparaptera  {IP  and  2P)^  while  one  or 
occasionally  two  are  similarly  situated  behind  the  wdng  processes 
and  are  the  epimeral  pavapteva  or  postparaptera  {3P  and  J^P).  The 
preparaptera  afford  insertion  for  the  muscle  concerned  in  the  exten- 
sion and  pronation  of  the  wing. 

The  coxa  (Cx),  or  basal  segment  of  the  leg.  is  hinged  to  the  seg- 
ment by  a  dorsal  articulation  wdth  the  pleural  coxal  process  (CxP), 
and  by  a  ventral  articulation  {TnC)  with  a  plate  called  the  trochan- 
tin  {Tn)  lying  in  front  of  it  and  connected  above  with  the  lower 
end  of  the  episternum  (Eps).  Hence,  while  the  leg  is  of  course  con- 
tinuous all  around  its  base,  by  means  of  membrane.  Avith  the  body- 
wall,  its  movement  is  limited  to  a  hinge  motion  by  these  two  special 
articulations  of  the  chitin. 

The  sternum  or  ventral  plate  of  the  segment  is  not  so  complicated  as 
are  the  tergum  and  pleurum.  It  is  often  divided  transversely  into 
three  parts,  however,  and  some  authors  say  typically  into  four.  These 
loarts  have  been  named  the  prestei'mim  (Ps),  sternum  proper  (S)^ 

segments  of  the  thorax  or  their  respective  parts.  Entomologists  have  already 
established  the  system  of  referring  a  part  to  the  front  or  back  of  any  individn.il 
segment  by  the  Latin  prefixes  pre  (or  prw)  and  post  as  nsed  in  "  prescutum," 
"  presternum,"  "  postscutellum,"  and  "  poststernellum."  Furthermore,  pre  and 
post  are  so  indiscriminately  used  in  English  combined  with  Latin,  Greek,  and 
even  Anglo-Saxon  words  that  they  may  be  regarded  as  general  property. 
Hence,  in  order  not  to  sacrifice  an  anatomical  system,  which  certainly  needs 
to  be  fostered  in  every  way,  the  writer  has  preferred  to  sacrifice  strict  gram- 
matical rules  by  applying  pre  and  post,  regardless  of  the  origin  of  the  noun 
in  the  case,  to  designate  anterior  and  posterior  parts  of  the  same  segment.  We 
already  use  such  hybrid  terms  as  "  presternum,"  '*  mesotergum,"  and  '*  meta- 
tergum." 

'J'he  name  "  proopistornum  "  has  been  applied  by  Hopkins  (Hul.  17,  Pt.  I, 
technical  series.  Bur.  Ent.,  U.  S.  Dept.  Agr.,  HUM))  to  a  part  of  the  mesepister- 
num  of  Dandroctonus — a  plate  apparently  not  homologous  with  the  proopisternal 
'.'lenient  of  the  thorax  in  primitive  insects. 

"The  name  "  parapterum  "  is  taken  from  Audouin's  term  />(//(/ />/r/r  (Ann. 
des  Sci.  Nat,  I,  1S24,  pp.  07-135,  416^32),  and  its  application,  as  useil  by  the 
l)resent  writer,  is  based  on  Audouin's  definition  given  in  his  Chapter  III, 
''  (U)nsiderationcs  gcnvralcs  sur  le  Thoru.v,"  where  he  says  (p.  122)  :  "Finally 
there  exists  a  piece  but  little  develoi)ed  and  seldom  observcnl.  connected  with 
both  the  episternum  and  the  wing.  It  is  always  supported  by  the  episternum 
and  is  sometimes  prolonged  ventrally  along  its  anterior  margin,  or  again, 
l>econiing  free,  i)asses  in  front  of  the  wing  and  may  even  come  to  lie  above 
the  base  of  the  latter.  ^  At  first  we  designated  this  sclerite  by  the  name  of 
Ifi/poptdrp  but  on  account  of  its  change  of  position  relative  to  the  wing  base 
w<?  now  prefer  the  name  of  Parapt^re."  The  first  part  of  his  description  leaves 
no  (loul)t  that  Audoiiiii  referred  to  the  liltle  pleural  plate  beneath  the  front 
of  the  wing  which  is  usually  very  inconspicuous  except  iu  carefully  dissected 


GENERAT.   EXTERNA!.   STRUCTURE    OF    INSECTS. 


21 


Emp' 


-CL 


Fig. 


-Typical   insect   log. 


.^teniellu?n  {jSI),  and  puststcriu'llnni  {PsI).  In  some  of  llic  lower 
insects  a  plate  {x)  occurs  at  each  side  of  the  prostcrnuni  or  of  the 
sternum  Avhich  seems  to  fall  in  line  with  the  preepisternum  of  the 
pleurum.  This  has  been  variously  called  a  part  of  the  presternum^ 
the  coxosternum^  an  accessory  sternal  plate^  and  the  sternal  laterale. 
The  inner  surface  of  the 
sternum  carries  a  large 
two- pronged  process 
called  the  furca  or  ento- 
stcrniim. 

This  plan  of  structure 
for  the  mesothorax  and 
the  metathorax  prevails 
throughout  all  insects. 
The  honey  bee  probably 
presents  the  greatest  de- 
parture from  it,  but  even 
I)ere  the  modification  consists  ^principally  of  a  suppression  of  the 
sutures  of  the  pleurum  resulting  from  a  condensation  of  the  parts. 

The  leg  (fig.  5)  of  an  adult  insect  consists  of  a  number  of  joints 
or  segments.    It  is  attached  to  the  body,  as  just  described,  by  a  thick 

specimens.  In  snch  jireparations.  however,  one  finds  that  there  are  in  most 
cases  two  sclerites  here  histead  of  one,  and,  furthermore,  that  one  or  occa- 
sionally two  others  are  similarly  situated  beneath  the  rear  part  of  the  wing 
base  behind  the  pleural  wing  process.  The  present  writer  has,  therefore, 
made  the  term  "  paraptera  "  cover  this  whole  row  of  little  plates,  distinguish- 
ing those  before  and  those  behind  the  pleural  wing  process  by  the  designations 
given  above. 

In  the  latter  part  of  Audouiu's  definition  it  would  seem  that  he  may  have 
confused  the  rudimentary  tegula  as  it  exists  in  some  insects  with  the  parapte- 
rum,  but  even  this  is  not  probable  since  he  says  it  is  always  connected  with 
the  episternum,  which  is  never  true  of  the  tegula.  In  his  description  of  the 
thorax  of  beetles,  Dytiscus,  Carahiis,  Biiprestis,  and  Curculio,  it  is  evident 
that  he  regards  the  anterior  upper  part  of  the  episternum  as  the  parapterum 
fused  with  the  latter  plate.  In  fact,  in  each  case  he  definitely  states  that  such 
is  the  case  and,  in  describing  Dytiscus  circumflc.rus,  he  says  (p.  420)  :  "The 
episternum,  the  parapterum,  and  the  epimerum  all  fuse  dorsally  and  constitute 
a  support  for  the  wings  and  tergum."  While  Audouin  is  undoubtedly  mis- 
taken in  this  homology,  especially  in  the  mesothorax,  he  at  least  shows  that 
his  "  paraptere "  is  a  part  of  the  pleurum.  Hence  modern  writers  such  as 
Packard  and  Folsom  who  make  the  term  "  paraptera "  synonymous  with 
"  tegulai "  are  certainly  wrong.  The  tegula  is  a  dorsal  scale  or  its  rudiment 
at  the  humeral  angle  of  the  wing,  while  the  parai)terum  is  a  co-existent  scle- 
rite  below  this  part  of  the  wing  base.  The  present  writer  agrees  with  Comstock 
and  Kellogg,  who,  in  their  Elements  of  Insect  Anatomy  (first  edition),  define 
the  little  sclerite  in  front  of  the  base  of  the  wing  in  the  locust,  articulated  to 
the  dorsal  extremity  of  the  episternum,  as  the  "  parapteron,"  though  in  this 
insect  there  are  here  really  two  of  these  parapteral  plates  instead  of  one. 


22 


THE    ANATOMY    OF    THE    HOXEY   BEE. 


basal  joint  called  the  coxa  {^Cx) .  Beyond  this  is  a  smaller  joint 
called  i\\^  trochanter  (Tr),  this  is  followed  by  a  long  and  strong 
i-eginent,  the  feni  ur  (F) ,  which  extends  outward  from  the  body,  while 
bending  downAvard  from  its  distal^ end  is  the  long  and  slender  tibia 
(Th).  followed  finally  b}'^  the  foot,  or  tar^sus  {Tar).  The  tarsus  itself 
consists  typically  of  five  small  segments  of  which  the  last  bears  a  pair 
of  claws  (Cla).  The  under  surfaces  of  the  tarsal  joints  are  often 
IDrovided  with  small  cushions  or  pads  called  pulvilli.  Those  between 
the  claws  are  generall}^  specially  prominent  and  are  called  the 
em  podia  {Emp).  The  leg  varies  greatly  in  shape  in  different  in- 
sects but  usually  preserves  all  of  these  parts.  The  segments  of  the 
tarsus,  however,  are  frequently  reduced  in  number. 

The  adult  wing  is  a  thin  expanse  of  membrane  supported  by  hollow 
branching  rods  called  veins.  It  originates  as  a  hollow  outgrowth  of 
the  bodv-wall,  but  soon  becomes  flattened  out  dorso-ventrallv  and  the 


Fk;.    <>. — Diagram   of  generalized   insect    wing   and    its   articulation    to   first   plate    (.V)    of 

the  tergum. 

contained  tracheae  or  air  tubes  mark  out  the  courses  of  the  veins. 
These  veins  form  various  patterns  in  different  insects,  but  they  can  all 
be  derived  by  modification  from  one  fundamental  plan.  This  i)lan  is 
shown  diagrammatically  by  figure  (>.  The  first  vein,  which  usually 
forms  the  anterior  margin  of  the  athilt  wing,  is  the  costa  (C).  The 
next  vein  is  the  subeosta  (Sc),  which  in  typical  cases  divides  into 
two  branches  (Sc^  and  Sc.,).  The  third  and  usually  the  principal 
vein  is  the  raditts  (/i).  It  divides  dichotomously  into  five  branches 
(/^,  to  /ir,),  the  anterior  branch  of  the  first  fork  remaining  single. 
The  next  vein  is  the  jnedia  (J/),  which  forms  four  branches  (.1/^  to 
J/,).  The  fifth  is  (he  cubitus  {(' n) ,  which  again  is  tAVo-branched. 
The  remaining  veins  are  called  the  anals  and  are  designat(Ml  indi- 
vidually as  (he  first  (tmd  {J A),  second  anal  (-M),  e(('. 

Several  cross- reins  of  coniinon  recurrence  should  be  n()(ed.  The 
first  is  sidiad'd  near  (he  base  of  (lie  wing  be(ween  (he  ('()s(al  and 
subcostal   veins  and  is  known  as  (he  /uinicr(d  cnjss-cein.     A  second 


GKNEHAL  EXTERNAL  STRUCTURE  OF  INSECTS.  23 

occurs  between  (he  radius  and  the  media  near  llie  center  ol'  the  win*^ 
and  is  called  the  I'adio-niedial  cross-vein.  Anolhei*  one,  the  niedio- 
ciihital.,  is  siniihirly  located  between  the  media  and  the  cubitus, 
while  a  fourth,  called  the  median,  occurs  between  the  second  and 
third  branches  of  the  media.  The  areas  of  the  win<;^  surface  inclosed 
by  the  veins,  the  cross- veins,  and  the  margins  of  the  wing  are  known 
as  the  cells. 

A  great  man}^  different  names  are  applied  by  different  entomolo- 
gists to  the  veins  of  the  wings,  both  of  the  same  and  of  different 
insects.  The  nomenclature  here  given  is  the  one  first  consistently 
applied  by  Comstock  and  Needham  and  now  used  by  a  large  number 
of  entomologists  working  in  different  orders  of  insects. 

The  Aving  is  articulated  at  its  base  (except  in  mayflies  and  dragon- 
flies)  to  the  anterior  and  posterior  wing  processes  of  the  notum 
(fig.  6,  ANP  and  PNP)  and  to  the  wing  process  of  the  pleurum  (fig. 
4,  WP)  by  several  small  articular  sclerites  called  axillaries.  Two 
of  these,  the  first  {lAx)  and  the  fourth  {J^Ax)^  form  a  hinge  with  the 
anterior  and  the  posterior  notal  wing  processes,  respectively,  while 
the  second  {2Ax)  articulates  below  with  the  wing  process  of  the 
pleurum,  constituting  thus  a  sort  of  pivotal  element.  The  third  axil- 
lary (SAx)  intermediates  between  the  bases  of  the  anal  veins  and  the 
fourth  axillary — except  Avhen  the  latter  is  absent  (as  it  is  in  nearly 
all  insects  except  Orthoptera  and  Hymenoptera),  in  which  case  it 
articulates  directly  with  the  posterior  notal  process.  The  thin  mem- 
brane of  the  wing  base  may  be  called  the  axillary  Tnemhrane  {xixAl). 
On  its  anterior  edge  is  a  hairy  pad,  the  tegida  (Tg)^  which  is  some- 
times a  large  scale  overlapping  the  humeral  angle  of  the  wing.  The 
posterior  margin  of  the  axillary  membrane  is  thickened  and  may  be 
called  the  axillary  cord  (AxC)  or  hasal  ligament  of  the  wdng. 

The  base  of  the  costa  is  not  directly  associated"  Avith  any  of  the 
axillaries,  but  is  specially  connected  by  tough  membrane  below  Avith 
the  episternal  paraptera.  The  subcosta  abuts  against  the  end  of 
the  curved  neck  of  the  first  axillary.  The  radius  is  either  attached 
to  or  touches  upon  the  anterior  end  of  the  second.  The  media  and 
cubitus  are  usually  associated  Avith  each  other  at  their  bases  and  also 
more  or  less  closely  Avith  one  or  tAvo  median  plates  (m)  in  the  Aving 
base.  These  plates,  hoAvever,  are  not  of  constant  shape  and  occur- 
rence as  are  the  articulating  axillaries.  The  anals  are  generally 
attached  to  the  outer  end  of  the  third  axillary,  Avhich  acts  as  a  lever 
in  the  folding  of  the  Aving. 

A  feAv  insects  have  a  generalized  Aving  almost  identical  Avith  the 
diagram  (fig.  G),  but  most  of  them  depart  from  it  in  varying  degrees. 
FeAv  go  so  far,  hoAvcA^er,  as  the  honey  bee,  Avhose  A-enation  is  A^ery 
different,  but  yet  the  fundamental  basal  structure  is  the  same  eA^en 


24  THE  AXATOMY  OF  THE  HONEY  BEE. 

here,  as  will  be  shown  in  the  special  description  of  the  wing  of  the 
bee. 

The  abdomen  consists  almost  always  of  10  segments.  There  are 
never  any  more  than  this  number  well  developed  in  adult  insects,  and 
if  there  are  fewer  the  reduction  is  dtie  to  a  modification  of  the  ter- 
minal segments  to  accommodate  the  external  organs  of  reproduction. 
The  posterior  opening  of  the  alimentar}^  canal  is  at  the  end  of  the 
tenth  segment,  which  carries  also  two  small  appendages  at  the  sides  of 
the  anus.  These  are  called  the  cerci  (fig.  8,  Cer) .  In  some  insects  they 
are  short,  styletlike  processes,  in  others  the}^  are  long  and  many 
jointed,  while  in  many  they  are  absent.  The  cerci  are  sttpposed  to 
be  develojDed  from  the  embryonic  appendages  of  the  tenth  segment, 
although,  on  the  other  segments,  these  appendages  disappear  before 
the  embryo  hatches,  except  in  some  members  of  the  lowest  wingless 
order  of  insects,  which  have  a  pair  of  cercuslike  appendages  on  each 
segment  of  the  abdomen. 

Each  abdominal  segment  presents  a  tergum  above  and  a  sternum 
below ;  the  former  usuall}^  also  reaches  far  down  on  the  sides  and 
overlaps  the  edges  of  the  sternum.  In  some  insects  one  or  more  small 
pleural  plates  intervene  between  the  tergum  and  the  sternum,  but 
the  abdominal  j^leura  are  never  developed  in  any  way  suggestive  of 
a  thoracic  pleurum.  Very  frequently  there  is  present  an  upper 
pleural  plate,  or  epipleiirite^  adjoining  the  edge  of  the  tergum  and  a 
lower,  or  hypopleiiHte^  adjoining  the  edge  of  the  sternum.  The  line 
separating  these  two  sclerites,  however,  is  horizontal  and  can  not 
correspond  with  the  vertical  stiture  of  a  thoracic  pleurum  between  the 
episternum  and  the  epimerum  extending  from  the  base  of  the  leg 
to  the  base  of  the  wing. 

The  most  complicated  structures  on  the  abdomen  are  the  external 
organs  of  reproduction.  In  the  male  these  serve  as  clasping  on/dns 
and  take  on  a  great  variety  of  forms  in  different  species.  The  organs 
in  the  female  form  an  ovipositor  and  are  of  nuich  more  definite  and 
constant  structure. 

The  oripositor  (fig.  8),  in  its  most  perfect  devel()i)ment,  consists  of 
three  pairs  of  long,  closely  appressed  bladelike  processes  called 
gonapophyses  (JG,  iJG,  SG),  These  six  pieces  fit  neatly  together  and 
form  an  organ  by  means  of  which  the  female  makes  a  hole  in  the 
ground  or  in  the  bark  of  a  tree,  or  punctures  some  other  insect,  and 
then  places  her  eggs  in  the  cavity  thus  produced.  An  interesting  fact 
in  this  connection  is  that  the  sting  of  a  wasp  or  bee  is  simply  a  modi- 
fied ovipositor.  This  can  l)e  proved  by  a  c()m})aris()n  of  the  organs 
themselves  or  hy  a  study  of  their  development.  Kach  is  formed  from 
six  little  j)eglike  processes  that  grow  out  from  the  sterna  of  the  eighth 
and  ninth  aljdominal  seijfments  of  the  larva  or  voung  soon  after  hatch- 


GENERAL   EXTERNAL   STRUCTURE    OF    INSECTS. 


25 


ing  (fig.  7,  IG^  2G^  and  oG).    At  first  llu'i'e  is  only  one  pair  of  those 
processes  on  each  of  the  two  segments,  but  those  on  the  ninth  soon 
split  each  into  t\Yo,  thus  producing  two  pairs  on  this  soginont.     The 
opening  of  the  oviduct   {0 uO)   is  on  the 
eighth  segment  between  the  bases  of  the 
first  gonapoph3^ses. 

The  ovipositor  of  the  longhorned  grass- 
hopper, shown  by  figure  8,  may  be  taken  as 
a  typical  example  of  this  organ.  The 
median  pair  of  gonapophyses  on  the  ninth 
segment  {^G)  remain  slender  and  fuse  at 
their  bases  into  a  small  bulblike  swelling 
open  below  (ShB).  The  pair  from  the 
eighth  segment  (IG)  form  tw^o  long  blade- 
like pieces,  which  fit  by  sliding  articula- 
tions upon  the  lower  edges  of  the  corre- 
sponding second  gonapophyses  {2G).  The 
first  can  therefore  be  worked  back  and 
forth  w^hile  they  are  braced  and  held  in 
position  by  the  second  pair.  The  third 
gonapophyses  {3G),  or  the  outer  pair  of 
the  ninth  segment  (the  left  one  in  figure  8  is  shown  as  if  cut  off  near 
its  base),  form  two  long  flat  blades  which  are  closely  appressed 
against  the  outer  surfaces  of  the  others.  In  the  detailed  study  of 
the  bee  it  will  be  shown  how  closely  the  structure  of  the  sting  corre- 
sponds in  every  way  with  that  of  this  ovipositor. 


An      2G 

Fig.  7. — Diagram  of  terminal 
abdominal  segments  of  a  fe- 
male insect  and  early  stage  in 
development  of  gonapophyses 
(IG,  2G,  and  3G),  from 
which  is  formed  the  ovi- 
positor of  most  insects  and 
the  sting  of  wasps  and  bees. 


Sp         3G  'C>  2G 

Fig.  8. — Example  of  a  swordlike  ovipositor,  from  a  longhorned  grasshopper  (Cono- 
cephalus  sp.),  illustrating  the  fundamental  similarity  of  structure  with  the  sting  of  the 
bee,  fig.  3G. 


Some  entomologists  have  supposed  that  the  original  two  pairs  of 
gonapophyses  represent  the  embryonic  appendages  of  the  eighth  and 
ninth  segments,  and  they  would  thus  establish  a  homology  between 
the  ovipositor  or  sting  and  the  legs  and  mouth  parts.  It  has  been 
shown,  how^ever,  that  the  true  appendages  of  the  abdominal  segments 
disappear  in  embryonic  life  while  the  gonapophyses  appear  much 
later,  during  early  nymphal  or  larval  life.     Furthermore,  each  pair 


^t)  THE    ANATOMY    OF    THE    HONEY   BEE. 

of  gonapophvses  arises  in  a  median  depression  on  the  ventral  side  of 
the  segment  while  the  true  appendages  are  latero-ventral.  Hence, 
the  evidence  is  very  much  against  this  theory  and  the  gonapophyses 
ajDpear  to  be  special  secondary  processes  of  the  body  wall. 

All  insects  do  not  have  ovipositors  of  the  sort  described  above. 
Flies,  beetles,  moths,  and  butterflies  do  not.  Such  insects  simply 
droj)  their  eggs  from  the  oritice  of  the  oviduct  or  deposit  them  in 
masses  upon  the  external  surfaces  of  various  objects.  In  some  of 
the  flies,  however,  the  terminal  segments  are  long  and  tubular  and 
entirely  telescoped  into  one  another.  They  are  hence  capable  of 
being  protruded  in  the  form  of  a  long  tapering  tube  having  the  open- 
ing of  the  oviduct  near  the  tip.  This  enables  the  insect  to  deposit  its 
eggs  in  deep  crevices,  but  the  structure  is  not  a  true  ovipositor — it  is 
simply  the  abdomen  itself  stretched  out. 

Insects  breathe  through  a  series  of  small  holes  situated  along  each 
side  of  the  body.  These  breathing  apertures  are  called  spiracles  and 
the}'  lead  into  a  system  of  internal  air  tubes  called  trachece.  There 
are  nearly  always  10  spiracles  present  on  each  side  of  the  body.  Two 
are  located  on  the  thorax,  the  first  between  the  prothorax  and  the 
mesothorax,  the  second  between  the  mesothorax  and  the  metathorax, 
while  the  other  eight  are  situated  on  the  first  eight  abdominal  seg- 
ments. Some  embryologists  believe  that  the  spiracles  of  the  pro- 
thorax  move  forward  in  early  embryonic  life  and  unite  with  each 
other  in  front  of  the  hypopharynx  to  form  the  salivary  opening,  their 
tracheae  constituting  the  salivary  ducts. 

After  this  review  of  the  general  external  structure  of  insects  we 
may  proceed  to  a  more  detailed  account  of  the  parts  and  organs  of 
the  honey  bee. 

III.    THE  HEAD  OF  THE  BEE  AND  ITS  APPENDAGES. 

The  head  of  an  insect,  as  already  explained,  is  a  composite  organ 
formed  of  six  or  seven  primitive  segments,  each  of  which,  except  the 
first,  typically  bears  a  pair  of  appendages  (fig.  2).  The  antenna^  are 
develojiCMl  from  the  embryonic  appendages  of  the  second  segment, 
the  mandibles  from  the  fourth,  the  maxilhe  from  the  sixth,  and  the 
second  maxilht',  or  labium,  from  the  seventh.  The  appendages  of 
the  third  segment  disappear  in  early  embryonic  life  while  those  of 
the  fifth  segment,  when  the  latter  is  present,  fuse  with  a  median 
tonguelike  lobe  of  the  next  segment  to  form  the  hypopharynx  of 
tlic  adult. 

1.    iiiK  srifrcrrK'i-:  of  vuk  iikad. 

'i'he  general  apj)earaiice  and  outline  of  the  head  of  a  worker  bee 
are  shown  from  before  and  behind  by  figure  9,  A  and  \\.  In  facial 
view  the  head   is  triangiihir,  with  the  aj)ex  l)eh)w.     The  side  angles 


THE    HEAD    OF    THE    BEE   AND    ITS    APPENDAGES. 


27 


are  rounded  and  capped  by  the  lar<i^e  compound  (»yes  (A').  In  the 
opposite  direction  the  head  is  very  much  flattened,  the  greatest  diamc^- 
ter  being  crosswise  through  the  middle  of  the  eyes.  The  face  is  con- 
vex, while  the  i^osterior  surface  is  somewhat  hollow^ed  out  and  fits 
snugly  upon  the  anterior  end  of  the  thorax. 

The  large  lateral  eyes  (fig.  9  A,  E)  are  called  the  compound  eyes, 
because  each  is  composed  of  a  large  number  of  separate  eye  elements 
forming  the  little  hexagonal  facets  visible  on  the  surface.  All  of 
these  facets  together  constitute  the  cornea^  or  the  transparent  outer 
surface  of  the  eye,  which  in  the  bee  is  densely  clothed  with  long  hairs. 
The  dark  color  of  the  eye  is  located  in  the  deeper  parts,  but  these  will 
be  described  in  the  section  dealing  Avith  the  nervous  system.     On  the 


Vx  P 


Vx  ten 


Ant 


PrbFs 


Gl/]/   Pgl 

Fig.  9. — A,  front  view  of  head  of  worker  bee  with  mouth  parts   (Pr6)    cut  off  a  short 
distance  from  their  bases  ;  B,  corresponding  view  of  posterior  surface  of  head. 

top  of  the  head  between  the  compound  eyes  are  the  three  simple  eyes, 
or  ocelli  (6>),  arranged  in  a  triangle  with  the  median  ocellus  in  front. 

Between  the  lower  halves  of  the  large  eyes  and  near  the  center  of  the 
face  arise  the  antennae  {Ant)^  each  of  which  is  inserted  into  a  small, 
circular,  membranous  socket  of  the  head  wall,  and  consists  of  a  long, 
basal,  1-segmented  stalk  carrying  a  terminal  11-jointed  arm  movably 
articulated  to  the  stalk  and  generally  hanging  downward  from  it. 
(In  the  drone  the  terminal  arm  consists  of  12  joints.) 

The  mouth  parts  are  attached  at  the  lower  part  of  the  head,  and 
consist  of  the  mandibles  {Md)  laterally  and  the  maxillce  {Mx) 
and  labium  {Lb)  mesially.  The  latter  two  include  the  set  of  elongate 
bladelike  organs  surrounding  the  protrusible  "  tongue,"  which  to- 
gether constitute  what  is  commonly  known  as  the  proboscis  {Prb). 


28  THE  ANATOMY  OF  THE  HONEY  BEE. 

"When  not  in  use  the  parts  of  the  proboscis  are  bent  back  beneath 
the  head.  By  referring  to  figure  9B,  giving  a  posterior  view  of  the 
head,  it  will  be  seen  that  the  basal  parts  of  both  the  maxillae  (St) 
and  the  labium  (Mt)  are  suspended  in  a  large  hollow  on  the  back  of 
the  craniimi.  This  may  be  called  the  cavity  or  fossa  of  the  proboscis 
(PrbFs).  Between  the  mandibles  on  the  front  of  the  head  (fig. 
9A)  is  a  transverse  movable  flap,  the  lahrum  {L?n),  attached  to  the 
lower  edge  of  the  front  wall  of  the  head  and  constituting  the  up})er 
lip.  The  mouth  {JIth)  lies  behind  the  labrum  and  the  mandibles 
close  beneath  it. 

Below  the  antennal  sockets  is  a  transverse,  slightly  arched  suture 
(a)  which  turns  downward  on  each  side  and  extends  to  the  inner 
angles  of  the  bases  of  the  mandibles.  The  area  bounded  by  this 
suture  is  the  dyjyeus  {Clj))  and  the  suture  itself  may  be  called  the 
clypeal  suture. 

On  the  posterior  surface  of  the  head  (fig.  9B)  is  seen  the  pen- 
tagonal foramen  magnum  {For)  by  means  of  which  the  cavity  of 
the  head  communicates  with  that  of  the  thorax  and  through  which 
pass  the  nerves,  oesophagus,  blood  vessel,  and  tracheal  tubes.  A 
small  rod  {ten)  inside  the  head  arches  transversely  over  the  fora- 
men magnum,  cutting  it  into  a  dorsal  and  a  ventral  half.  At  each 
side  of  the  foramen  is  a  large  pit  (c)  which  marks  the  base  of  an 
internal  chitinous  beam  of  the  head  known  as  the  mesocephalic  pillar. 
The  opposite  end  of  this  pillar  unites  with  the  front  wall  of  the 
head  on  the  clypeal  suture  below  the  antenna?,  where  it  produces 
another  smaller  pit  {h). 

BeloAv  the  foramen  magnum  and  separated  from  it  by  a  wide  trans- 
verse bridge  of  the  cranial  wall  is  seen  the  large  fossa  of  the  proboscis 
(fig.  9B,  PrhFs)  having  the  shape  of  an  inverted  U.  The  side  walls 
of  this  cavity  are  chitinous  and  from  their  upper  edges  are  suspended 
the  maxilla^,  while  the  base  of  the  labium  is  contained  in  the  mem- 
branous floor  of  the  fossa.  The  base  of  the  labium  projects  from  the 
head  beneath  or  behind  the  mouth  opening  and  its  dorsal  surface 
forms  the  floor  of  a  preoral  cavity  surrounded  by  the  bases  of  the 
mouth  parts  and  labrum. 

It  will  be  seen  from  the  above  descri})tion  that  the  head  wall  of  the 
bee  contains  no  suture  except  that  bounding  the  clypeus  and  the  one 
which  separates  the  labrum  from  the  latter.  Many  of  the  high<M' 
insects  have  the  head  wall  completely  continuous,  showing  no  div'ision 
at  all  into  sclerites,  l)ut,  in  such  forms  as  a  grasshopper  or  cockroach, 
and,  in  fact,  most  of  the  lower  insects,  the  head  as  well  as  the  other 
parts  of  the  body  is  made  up  of  a  number  of  plates.  Hence  this  may 
be  regarded  as  the  primitive  condition,  and  it  is  presumed  that  the 
head  of  the  bee  lias  been  pi'oduced  fi'om  one  wliose  wall  was  divided 
by  sutures  into  a  nuiiibci'  of  distinct  parts.     Therefore  the  difl'crent 


THE    HEAD    OF    THE    BEK    AND    ITS    ADI'KN  DA(;ES. 


29 


iCi. 


iMdCl 


i'Oi>-ioiis  of  the  beo's  head  inav  1)(>  named  accord iii<z"  lo  llic  -cleriles  with 
which  they  coiTespond  in  other  insects.  Thn>,  the  part  of  tlie  face 
above  the  clypeus  and  between  the  compound  eves  may  be  called  the 
front  (fig.  9A,  Ft)^  the  parts  below  the  compound  eyes  the  f/enw  {Ge)^ 
and  the  top  of  the  head  the  vertex 
{V,r).  The  area  on  the  back  of  the 
head  around  the  foramen  magnum 
ma}^  likewise  be  termed  the  occipital 
region  (tig.  OB,  Oc)  and  the  parts  be- 
hind the  ffena?  and  the  lower  halves 
of  the  compound  eves  the  j^ostgence 
iPge). 

The  worker,  queen,  and  drone  differ 
conspicuoush^  in  the  shape  and  size  of 
the  head,  as  will  be  seen  by  comparing 
A.  B.  and  C  of  figure  10.  In  these 
drawings  the  front  has  been  removed 
in  order  to  show  various  internal 
parts,  which  will  be  described  later. 
While  the  head  of  the  worker  (A)  is 
triangular  in  facial  view,  that  of  the 
queen  (B)  is  more  rounded  and  wider 
in  proportion  to  its  length.  The  head 
of  the  drone  (C)  is  much  larger  than 
that  of  the  female  and  is  nearly  cir- 
cular in  outline.  In  shape  the  head 
of  the  queen  is  intermediate  between 
that  of  the  worker  and  that  of  the 
drone,  but  in  size  it  is  somewhat 
smaller  than  the  head  of  the  worker. 
The  eyes  {E)  of  the  worker  and  queen 
are  about  equal,  but  those  of  the  drone 
are  enormously  enlarged  and  are 
broadly  contiguous  on  the  vertex  and 
the  upper  part  of  the  front.  On  this 
account  the  ocelli  ((9)  of  the  drone  are 
crowded  down  on  the  front  nearer  the 
bases  of  the  antenna?  and  the  front 
itself  is  very  much  narrowed  above. 
The  antenna^  of  the  drone  consist  of 
13  segments,  while  those  of  the  females 
have  but  12  segments.  The  mandibles  are  largest  proportionatel}^  in 
the  queen  and  are  very  small  in  the  drone.  Those  of  the  worker  have 
a  smooth  terminal  edge,  while  this  edge  is  notched  in  the  queen  and 
the  drone.     The  parts  of  the  proboscis  are  much  longer  in  the  worker 


iMdCI 


Fig.  10. — A.  anterior  view  of  head  of 
worker,  witii  front,  antennae,  and 
proboscis  removed  ;  B,  correspond- 
ing view  of  liead  of  queen  ;  C,  same 
of  drone. 


30 


THE   AXATOMY    OF    THE    HOXEY   BEE. 


and  capable  of  much  more  action  than  in  the  queen  and  drone,  which 
are  almost  entirely  dependent  upon  the  workers  for  their  food. 

The  internal  structure  of  the  cranium  may  be  studied  best  in  a  longi- 
tudinal section  of  the  head  (fi<r.  H)-  In  order  to  prepare  a  section 
for  this  purpose  imbed  the  head  in  paraffin  and  then  carefully  slice 
off  one  side  with  a  sharp  knife  or  razor  just  outside  of  the  bases  of 
the  mandible  and  antenna.  Holding  the  remainder  in  the  block  of 
paraffin  or  fastening  the  whole  in  a  dish  of  water  or  alcohol,  care- 
fully dissect  away  the  soft  parts  from  the  head  cavity  so  as  to  expose 


Fio.  11. — A,  longitudinal  section  throujj:li  hoad  of  worker  bet\vi>ou  tlu>  incnlian  plaiu^  and 
outer  edges  of  mandibles  (.1/^/)  and  antenna'  (Ani)  of  left  side,  all  internal  soft  parts 
r(>moved :  B,  corresponding  section  through  hoad  of  drone,  except  that  the  pharynx 
(/'//?/)   and  (rsoi)hagns   {(JJ)  are  not  r(>nioved. 

the  inteinal  chitinous  j)arts  shown  in  ligure  11  A  and  B.  Thcsc^ 
figures,  however,  repi-esent  a  slice  of  the  head  taken  from  between  the 
median  })lane  and  tlie  outer  edges  of  the  niitennnl  ;ind  mandibular 
bases  of  the  left  side.  Thus  only  the  parts  on  one  side  of  the  mid- 
line are  shown.  Figure  A  is  from  a  worker  and  Figure  B  from  a 
(hone.  In  tlic  latter  the  pharynx  and  (esophagus  are  retained  and 
the  ne<-k  is  not  removed.  Figuiv  liO  shows  the  head  cut  open  from 
above  and  the  mouth  parts  removed,  A  s[)ecimen  so  cut  and  boiled 
a  short  time  in  cMiislic  soda  or  potash  to  remoxc  the  soft  parts  will 
1m'  found  a  \alu:il)h'  adjiincl  to  this  study. 


TIIK    1 1  KM)    OF    THK    BEE    AND    ITS    APJ'ENDAGES.  3  I 

The  pi'iiicipul  parts  of  the  iiilenial  skeleton  ol"  I  lie  head,  or  ado- 
cvaniu7ri^  consist  of  two  large,  oblique,  stron<^ly  (^hitinous  bars  form- 
ing a  brace  between  the  anterior  and  the  posterior  walls  of  the  liead 
(fig*.  11  A  and  B,  Ten^  showing  the  parts  on  the  left  side  only,  and 
fig.  19,  Ten).  These  bars  have  been  named  by  Macloskie  (1881)  the 
'inesocephalic  pillars.  As  already  pointed  out  the  base  of  each  is 
marked  externally  by  a  conspicuous  pit  (fig.  9  B,  c)  laterad  of  the 
foramen  magnum,  and  its  facial  end  by  a  smaller  pit  (fig.  9  A,  h) 
in  the  clypeal  suture  near  the  upper  end  of  each  side  of  the  latter. 
The  bases  of  these  pillars  are  connected  by  the  slender  bar  (fig.  11  A, 
ten)^  already  noticed,  arching  over  the  foramen  magnum  (fig.  9  B, 
ten).  This  bar  and  the  two  pillars  represent  what  is  called  in  other 
insects  the  tentorinm.  In  the  embryo  the  tentorium  is  formed  from 
tubular  ingrow^ths  of  the  head  wall  which  unite  internally  and 
assume  different  shapes  in  different  insects.  Since  the  air  tubes  of 
the  body  also  first  appear  as  tubular  ingrowths  of  the  body  wall, 
some  entomologists  have  supposed  that  the  hollow  tentorial  in- 
growths of  the  head  represent  the  spiracular  tubes  of  the  head 
which  are,  otherwise,  lacking.  However,  there  is  not  sufficient  evi- 
dence to  suj^port  such  a  vicAv  as  this,  and  there  is  no  reason  why  the 
tentorium  should  not  have  been  originally  designed  simply  to  give 
greater  rigidity  to  the  walls  of  the  head  where  the  latter  support  the 
appendages. 

The  usual  form  of  the  tentorium  in  the  lower  insects  is  that  of  an 
X,  w^ith  a  large  central  body,  situated  like  a  brace  across  the  lower 
part  of  the  head,  having  tw^o  of  the  arms  directed  anteriorly  and 
laterally  and  tw^o  directed  posteriorly  and  laterally,  and  while  the 
former  are  said  to  be  ingrowths  from  the  mandibular  segment,  there 
is  some  dift'erence  of  opinion  concerning  the  segment  to  which  the 
latter  belong.  Riley  states  that  they  are  formed  in  the  labial  seg- 
ment of  the  cockroach  and  Carriere  and  Burger  describe  the  same 
thing  for  the  mason  bee.  Other  authors  have  ascribed  them  to  the 
maxillary  segment,  but  they  may,  in  later  stages,  lie  in  this  segment 
and  thus  appear  to  belong  to  it,  while  they  originated  in  the  one 
following,  having  moved  forward  on  account  of  the  condensation 
of  the  back  part  of  the  head.  The  tentorium  of  the  honey  bee, 
consisting  as  it  does  of  the  two  great  mesocephalic  pillars  (fig.  11 
A  and  B,  Ten)  and  the  small  arched  bar  {ten)  is  so  highly  modified 
that  it  is  hard  to  see  just  how  its  parts  are  to  be  homologized  with 
the  parts  of  an  X-shaped  tentorium.  Probably  the  two  pillars  repre- 
sent the  separated  halves  of  the  X,  while  the  slender  arch  is  an  addi- 
tional structure.  In  any  case  we  have  not  enough  evidence  to  war- 
rant us  in  regarding  the  tentorial  invaginations  as  modified  tracheae, 
or  their  external  pits  as  rudimentary  spiracles.  Similar  processes 
extend  inward'  from  the  walls  of  the  thorax  to  strengthen  it  or  to 
give  attachment  of  muscles.     Such  processes  in  general   form  the 


32  THE  AXATOMY  OF  THE  HONEY  BEE. 

eiitoskeleton  and  are  individual^  called  apodemes.  Those  of  the 
head  constitute  the  entocranium^  those  of  the  thorax  the  entothorax. 

The  side  walls  of  the  fossa  of  the  proboscis  form  two  high,  thin, 
vertical  plates,  as  seen  from  the  interior  of  the  head  (fig.  11),  in 
front  of  the  mesoce]3halic  pillars.  The  posterior  edge  {d)  of  each 
of  these  plates  is  so  much  thicker  than  the  rest  of  it  in  the  worker 
that  it  appears  at  first  sight  to  be  a  separate  rod.  Its  upper  end 
projects  above  the  body  of  the  plate  as  a  free  arm  {e)  to  which  is 
articulated  the  basal  piece  of  the  maxilla  {Cd).  It  thus  constitutes 
the  maxillary  suspensorhnn.  (Macloskie  includes  under  this  term 
both  the  arm  of  the  cranial  wall  and  the  cardo  of  the  maxilla.) 

The  head  of  the  drone  (fig.  11  B)  presents,  besides  the  parts  de- 
scribed, a  thin  plate  (/)  depending  from  the  vertex  of  the  cranium 
along  the  line  between  the  compound  eyes. 

Besides  these  apodemes  of  the  cranial  wall  itself  there  are  others 
which  project  into  the  head  cavity  from  the  bases  of  the  appendages 
to  afford  points  of  insertion  for  their  muscles.  These  are  specially 
developed  in  connection  with  the  mandibles  and  will  be  described  in 
the  discussion  of  these  organs.  Still  other  internal  chitinizations  are 
developed  in  the  walls  of  the  pharynx,  but  these  likewise  will  be 
described  later. 

"1.    THE   ANTENNAE   AND   THEIR   SENSE   ORGANS. 

The  antenna?  of  the  bee  are  the  two  slender,  jointed  appendages 
movably  attached  to  the  center  of  the  face,  where  each  is  inserted 
into  a  circular  membranous  area  or  socket  just  above  the  upper  part 
of  the  clypeal  suture.  Their  general  shape  and  position  are  shown 
by  figures  9  A,  11  A,  and  19,  Ant,  Each  is  seen  to  consist  of  two 
parts,  forming  a  prominent  elbow  with  each  other,  and  usually  so 
held  that  the  first  or  proximal  part  extends  outw^ard  and  upward 
from  its  frontal  attachment  and  carries  the  other  in  a  pendent  posi- 
tion from  its  distal  end.  The  first  part  thus  forms  a  basal  stalk, 
called  the  scape  (figs.  9  A;  19,  Sep),,  consisting  of  a  single  joint 
inserted  into  the  antennal  socket  of  the  front  by  a  prominent  basal 
condyle  bent  toward  the  face.  This  articular  knob  is  attached  to 
the  rim  of  the  socket  by  a  circle  of  membrane,  but  it  is  also  pivoted 
on  a  slender  peglike  process  projecting  upward  from  the  lower  edge 
of  the  socket.  Hence,  while  the  flexible  membrane  allows  each 
antenna  to  i-evolve  freely  in  any  direction,  the  latter  is  at  the  same 
time  hehl  finidy  in  position  by  the  pivot.  The  antennne  are  moved 
\)\  special  sets  oi'  muscles  inserted  upon  theii-  bases  within  the  head. 
The  second  or  distal  division  of  the  antenna  is  cylindrical  and  longer 
llian  tlie  first,  forming  a  fh'\il)le  f(i(/<]hun  (fig.  9  A;  19,  Fl)  hanging 
downward  from  the  dist'il  end  of  the  scape.     It  ib  composed  of  11 


THE   HEAD   OF    THE    BEE   AND    TTS   APPENDACJKS.  33 

small  joints  in  tlie  worker  and  queen  and  of  12  in  the  drone.  The 
male  antenna  thus  consists  of  13  joints  in  all,  while  that  of  the  female 
has  but  12.  The  first  joint  of  the  flagellum  is  freely  articulated  to 
the  scape,  but  the  others  do  not  have  much  play  upon  one  another, 
though  they  give  flexibility  to  the  flagellum  as  a  whole. 

Each  antenna  is  a  hollow  tube  containing  the  large  antennal  nerve, 
minute  extensions  of  the  tracheal  system,  and  the  small  muscles  w^hich 
move  the  segments  upon  one  another. 

l\)pularly  the  antennae  of  insects  are  known  as  the  "  feelers,"  be- 
cause they  are  constantly  moved  about  in  all  directions  with  a  nervous 
kind  of  motion  as  if  the  creature  were  feeling  its  way  along  by  means 
of  them.  In  fact  "  feelers  "  is  a  better  name  for  these  appendages 
than  the  scientific  term,  for  there  can  be  no  doubt  that  the  sense  of 
touch  is  very  highly  developed  in  them  and  that  by  means  of  them 
insects  acquire  a  great  deal  of  information  concerning  their  surround- 
ings and  their  companions.  Moreover,  a  large  mass  of  evidence 
derived  from  experiments  show^s  unquestionably  that  the  organs  of 
smell  also  are  located  upon  the  antennse  in  a  great  many  if  not  all 
insects,  while  some  investigators  believe  that  in  some  species  they 
carry  in  addition  the  organs  of  hearing. 

The  study  of  the  senses  of  insects  is  a  most  elusive  subject,  and 
becomes  more  so  the  more  ^ve  ponder  on  the  results  of  experiments. 
In  the  first  place,  it  is  manifestly  impossible  for  us  to  acquire  any 
real  knowledge  of  an  insect's  sensations,  for  wdiat  is  to  us  an  odor, 
a  taste,  a  color,  or  a  sound  may  be  something  quite  different  to  such  a 
differently  organized  creature.  We  can,  however,  by  experiments 
determine  that  some  things  which  give  us  the  sensation  of  an  odor 
are  perceived  also  b}^  insects  w^hen  placed  near  them.  Also  it  can  be 
showm  that  some  of  them  distinguish  substances  of  different  taste  in 
their  food,  and  likew-ise  that  they  perceive  movement  and  distinguish 
the  colors  and  in  a  vague  way  the  outlines  of  objects.  Furthermore, 
it  is  known  that  some  of  their  perceptions  are  more  delicate  than  ours, 
and  that  some  insects  at  least  see  color  where  we  see  none.  They  may 
even  possess  senses  of  which  we  have  no  conception. 

Hence,  while  it  can  be  positively  stated  that  insects  perceive  differ- 
ences of  touch,  taste,  smell,  sound,  and  light,  and  act  accordingly,  we 
can  not  say  what  the  sensations  they  acquire  are  like.  In  fact  we 
do  not  know^  that  they  have  conscious  sensations  at  all.  What  looks 
like  an  action  due  to  intelligent  perception  may  be  purely  a  reflex  one, 
unaccompanied  by  any  sensation.  This  of  course  involves  the  ques- 
tion as  to  whether  such  creatures  or  insects  are  possessed  of  conscious- 
ness or  not — a  question  which  can  not  be  answered  one  way  or  the 
other. 

I^nderstanding,  then,  that  our  knowledge  of  insect  senses  amounts 
only  to  this,  that  what  gives  us  the  sensation  of  light,  sound,  taste, 
22181— No.  18—10 3 


34  THE  ANATOMY  OF  THE  HONEY  BEE. 

touch,  or  smell  makes  also  some  sort  of  an  impression  on  the  insect 
and  varies  in  degree  arid  kind  much  as  it  does  in  us,  we  may  go  on  to 
a  study  of  the  senses  located  on  the  antennae. 

Here,  again,  however,  we  are  confronted  by  a  difficulty,  for  while, 
at  first  thought,  it  seems  very  easy  to  hold  some  strong-smelling  sub- 
stance near  the  antennae  of  a  beetle,  ant,  or  bee  and  observe  the  evident 
displeasure  with  which  the  creature  turns  away,  j^et  we  may  be  en- 
tirely wrong  if  we  conclude  that  the  insect  "  smells  "  the  substance 
that  repels  it.  Strong-smelling,  volatile  liquids  may  simply  produce 
pain  in  some  of  the  delicate  nerve  endings  of  the  antennae.  Some 
other  kind  of  a  being,  experimenting  on  our  senses,  might  close  up 
our  nose  and  mouth  and  prove  that  we  smell  by  means  of  our  ej^es 
on  observing  the  blinking  we  should  perform  when  strong  formalin 
or  ammonia  was  held  close  to  the  face.  Furthermore,  irritant  gases 
and  volatile  liquids  affect  the  mucous  membranes  of  our  noses  and 
throats  in  a  way  quite  independent  from  the  odor  that  Ave  perceive, 
and  there  is  no  reason  why  the  same  may  not  be  true  of  insects.  As 
pointed  out  by  Forel,  experiments  on  the  sense  of  smell  should  be 
made  with  odorous  substances  that  the  insect  meets  with  in  a  state  of 
nature,  which  Avould  be  principally  the  materials  it  feeds  on.  In- 
sects are  indifferent  to  almost  every  mildly  odorous  substance  not 
used  as  food,  which,  however,  does  not  prove  that  they  do  not  smell 
them. 

Again,  in  many  cases,  it  would  be  difficult  to  decide  whether  the  re- 
sults of  an  experiment  should  be  accredited  to  smell  or  sight.  For 
example,  every  bee  keeper  knows  that  hungry  bees  are  attracted  to 
honey  a  long  distance  from  their  hives,  and  it  would  seem  almost  self- 
evident  that  they  are  guided  by  a  sense  of  smell.  Yet  one  might  con- 
tend that  they  find  the  honey  by  sight,  as,  indeed,  is  claimed  by  a 
fuimber  of  entomologists  Avho  have  made  experiments  on  the  olfactory 
powers  of  bees.  This  question  has  been  decided  in  scmie  other  insects 
by  painting  the  eyes  with  some  opaque  substance  or  by  removing  the 
antenna*,  but  the  evidence  is  not  conclusive  on  either  side  in  the  case  of 
bees. 

Experiments  made  by  a  large  number  of  competent  investigators, 
including  Lubb(K'k,  Schiemenz,  and  Forel,  have  ])r()ved  conclusively 
that  the  organs  of  the  sense  of  smell  in  insects  aie  locattMl  i)rin('ipally 
on  the  antenna'.  The  most  interesting  of  these  exiMM'inients  are  per- 
hai)s  those  which  Foi'el  (HKKi)  made  on  carrion-feeding  beetles.  He 
found  the  dead  and  putrid  bodies  of  a  hedgehog  and  a  rat  infested  by 
a  swarm  of  these  beetles  belonging  to  several  genera,  lie  collected 
more  than  40  specimens  fi-oni  the  carcasses  and  removed  their  an- 
tennae. Then  he  placed  them  all  at  one  place  in  the  grass  and  moved 
the  dead  bodies  to  a  distance  of  '28  paces  from  the  beetles  where  he 
concealed  them  in  a  tangle  of  weeds.     Examination   the  next  day 


THE    HEAD   OF    THE    BEE    AND    TI'S    APPENDAGES.  35 

revealed  the  fact  that  not  one  of  the  mutihited  beetles  had  found  the 
carcasses.  Repeated  experiments  gave  the  same  results — no  beetle 
without  its  antenna'  was  ever  found  on  the  dead  animals,  although  at 
each  examination  new  individuals  of  the  several  species  were  present. 
It  might  be  supposed  that  the  mutilation  itself  distracted  the  beetles 
to  such  an  extent  that  they  did  not  care  to  eat.  In  order  to  test  this 
point  Forel  next  cut  off  all  the  feet  on  one  side  of  the  body  from  a 
dozen  intact  beetles  and  changed  the  location  of  the  dead  bodies  again. 
The  next  day  five  of  this  lot  were  found  on  the  carcasses. 

The  same  results  have  been  obtained  from  experiments  on  other 
insects.  Ants  distinguish  between  their  comrades  and  enemies  by 
means  of  their  antennal  sense  organs.  Males  of  the  silkworm  moth 
and  many  other  moths  and  butterflies  perceive  the  presence  of 
the  females  and  are  guided  to  them  by  an  evident  sense  of  smell 
located  on  the  antennae,  for  they  fail  completely  to  find  them  when 
these  appendages  are  removed,  although  one  immediately  recognizes 
a  female  when  placed  in  contact  with  her. 

Similar  experiments  have  been  made  on  the  bee,  testing  the  ability 
of  the  Avorkers  to  find  honey  hidden  from  their  sight.  The  results, 
according  to  Forel,  seem,  curiously  enough,  to  indicate  that  bees  can 
perceive  odors  but  a  very  short  distance  from  their  heads.  Forel 
found  that  hungry  bees  in  a  cage  would  pass  and  repass  hundreds  of 
times  Avithin  a  fcAv  millimeters  of  some  honey  concealed  from  their 
sight  by  a  lattice  without  discovering  it.  They  ate  it  greedily,  how- 
ever, Avhen  the  lattice  w^as  removed,  though  it  had  been  perfectly 
accessible  to  them  all  the  time.  Forel  believes  that  "  bees  guide  them- 
selves almost  exclusively  by  vision,"  and  Lubbock  holds  the  same 
opinion.  At  the  same  time  it  would  probably  be  a  very  difficult  mat- 
ter to  convince  many  practical  bee  keepers  that  bees  do  not  ''  smell  " 
from  long  distances.  It  is  a  Avell-knoAvn  fact  that  at  times  when  nec- 
tar is  scarce  bees  are  attracted  in  large  numbers*  to  the  houses  of  an 
apiary  Avhere  honey  is  stored,  though,  when  the  natural  flow  is  suf- 
ficient, they  pa}^  no  attention  to  it.  Tests  of  the  olfactory  sense  should 
undoubtedly  be  made  under  natural  conditions.  Bees  inclosed  in  a 
box  with  some  honey  concealed  from  their  sight  might  not  be  able  to 
locate  it  in  such  close  quarters  though  they  might  be  smelling  it  all 
the  time.  An  odor  in  a  room  may  so  fill  the  air  that  it  does  not  seem 
to  come  from  any  particular  direction  and  we  ourselves  would  have 
to  exert  our  intelligence  to  discover  its  source. 

While,  then,  it  does  not  seem  probable  that  bees  have  such  limited 
olfactory  powers  as  some  investigators  claim  their  experiments  indi- 
cate, it  may  be  accepted  as  proved  that  the  organs  of  smell  are  located 
principally  on  the  antenna\  It  has  already  been  stated  that  the  sense 
of  touch  also  is  very  highly  developed  on  these  organs,  although  in  a 
less  sensitive  degree  it  is  distributed  over  most  of  the  other  parts  of 


36 


THE   ANATOMY   OF    THE    HONEY   BEE. 


the  body.    It  is  again  specially  developed  on  the  palpuslike  append- 
ages of  the  sting.     (See  figs.  36  and  37,  StnPlj}.)     Sections  of  a  bee's 

antenna  show  that  there  are 
on  its  surface  a  great  number 
of  minute  structures  of  sev- 
eral different  kinds,  though 
all  apparently  are  to  be  re- 
garded as  modified  hairs, 
which  are  undoubtedly  the 
sense  organs.  Xow  the  diffi- 
culty arises  of  deciding  which 
of  these  to  assign  to  the  sense 
of  touch  and  which  to  the 
sense  of  smell.  Different  au- 
thors have  made  such  differ- 
ent interpretations  of  the 
sense  organs  of  insects  that 
the  student  attempting  to  get 
information  on  the  subject 
from  books  must  soon  be  dis- 
couraged by  their  conflicting 
statements.  But  it  must  be 
realized  that  only  intelligent 
guessing  is  possible  where 
several  senses  are  located  on 
the  same  part.  In  the  case  of 
the  bee  some  authors  have 
ascribed  even  a  third  sense, 
that  of  hearing,  to  the  an- 
tenna\  but  there  is  little  evi- 
dence that  bees  possess  the 
power  of  hearing.  The  senses 
of  taste  and  touch  are  pos- 
sessed by  the  mouth  parts, 
and  some  entomologists  think 
that  they  contain  organs  of 
smell  also.  Thus,  the  organs 
of  sight  are  :4)i)arently  the 
only  ones  that  can  not  be  con- 
fused with  SOUK'  other  sense. 
The  best  account  of  the 
antennal  sense  organs  of  the 
bee  is  tliat  of  Schicmcuz  {bSSI)).  whose  (h-awiugs  ;ire  here  reproduced 
(fig.   VI)   and  whose  text   is  the  basis  of  the  foUowiug  (U'scriptions. 


Fig.  12. — Antennal  hairs  and  sense  organs 
(after  Scbieiuenz).  A,  exami)lo  of  antennal 
hairs  (//r)  imbedded  in  cutii-le  (Cf/)  but 
iiavin^'  no  nerve  connection  ;  11.  hollow  liair 
containin};  prolongation  of  special  cell  (T/i  ; 
C,  D,  straight  and  curved  tactile  hairs  con 
nected  with  basal  cells  {CI)  and  nerve  fibers 
(Xv)  ;  E,  conical  hair  illr)  sunken  in  a  pit 
(/'/)  of  the  cuticle,  probably  an  olfactory 
organ ;  V,  dosed  sac  shut  in  by  thin  disc 
(///■)  on  surface  of  antenna  and  containing  a 
delicately  poised  cell  (r/)  with  nerve  con- 
ned ion    (Sr). 


The  orirans  consist,  as  before  stated,  of  modified  hair.^ 


and 


their  basal 


THE    HEAD    ()!•    THK    P.KE    AND    ITS    APPENDAGES.  37 

insertions  which  are  conneeled  willi  the  ends  of  nerve  IUkm-s.  Sonic 
of  them  stand  exposed  on  the  surface  of  the  cuti(de  while  others 
are  sunken  into,  or  entirely  concealed  within,  pits  of  the  integument. 
In  addition  to  these,  there  are  two  other  kinds  of  special  hairs  on 
the  antennae  which  have  no  nerve  connections,  while,  finally,  the  ordi- 
nary hairs,  such  as  are  found  on  all  i)arts  of  the  body,  occur  also  on 
them,  especially  on  the  scape. 

The  special  hairs  not  provided  with  nerve  endings  are  of  two 
sorts.  One  is  a  solid  curved  or  hooked  hair  (fig.  12  A,  Hr)  wdiich 
is  simply  articulated  into  a  socket  of  the  cuticle  {Ctl).  w^hile  the 
other  (B)  is  hollow  and  is  situated  over  a  channel  through  the  cuticle, 
and  contains  a  prolongation  of  a  specially  enlarged  epithelial  cell 
{CI)  lying  beneath  it.  These  hairs  can  not  be  regarded  as  sensory, 
since  they  have  no  communication  with  the  central  nervous  system, 
and  it  is  not  clear  just  what  purpose  they  do  serve. 

The  simplest  sensory  organ  is  a  short,  hollow,  conical  hair  (C, 
TIr)  arising  directly  from  the  surface  of  the  cuticle,  over  a  wide 
opening  through  the  latter,  and  containing  the  end  of  a  sensory  cell 
(CI)  connected  with  a  nerve  fiber  {Nv)^  wdiich  goes  into  the  main 
trunk  of  the  axial  antennal  nerve.  A  modified  form  of  this  organ 
consists  of  a  curved  hair  (D,  H?')  set  into  a  small  depression  over 
the  cuticular  channel.  Such  hairs  are  probably  tactile  in  function; 
that  is  to  say,  by  means  of  them  the  bee  can  perceive  that  its  antennae 
are  in  contact  with  some  surface.  The  general  integument  is  too 
thick  and  dense  to  allow  of  any  sort  of  delicate  touch  sensation  being 
communicated  through  it,  but  if  one  of  these  movable  hairs  brushes 
against  an  object  the  nerve  within  it  must  be  at  once  stimulated. 
Tactile  or  touch  hairs  are  distributed  especially  over  the  outer  sur- 
face of  the  antennie  and  at  its  apex,  but  occur  also  scattered  over 
the  other  parts  of  the  body  and  on  the  mouth  parts. 

Microscopic  sections  of  the  antennae  reveal  still  other  organs 
which  are  not  so  apparent  on  the  surface  as  the  hairs  just  described. 
One  of  the'^e  is  shown  at  E  of  figure  12.  It  consists  of  a  small  pit 
(Pt)  in  the  integument,  widened  basally,  and  having  a  small  papilla 
on  its  floor,  in  whose  summit  is  the  opening  of  a  still  deeper  cavity 
which  also  expands  toward  its  deeper  end.  This  inner  cavity  is 
almost  filled  up  by  a  conical  plug  {Hr)  which  arises  from  its  floor 
and  ends  just  below^  the  aperture  into  the  outer  pit.  The  plug  con- 
tains a  thick  nerve  ending  which  arises  from  a  ganglion  cell  con- 
nected Avith  the  antennal  nerve  by  a  nerve  fiber.  Ten  or  more  of 
these  sense  organs  occur  on  the  terminal  and  the  first  three  segments 
of  the  flagellum.  It  is  evident  that  each  is  simply  a  sensory  hair 
which  has  been  doublv  sunken  into  a  cavitv  of  the  intes^ument. 


88        '     THE  ANATOMY  OF  THE  HONEY  BEE. 

As  before  stated,  it  has  been  conclusively  proved  by  several  investi- 
gators that  bees  perceive  odors,  and  it  is  said  that  if  the  antenna^ 
are  covered  with  shellac,  bees  can  distinguish  between  distasteful 
substances  only  by  means  of  the  proboscis.  Schiemenz  and  most 
other  writers  on  the  subject  therefore  conclude  that  the  sunken  cones 
are  the  organs  of  smell,  since,  being  below  the  surface,  they  could  not 
be  organs  of  touch.  Some  other  authors,  however,  among  whom  are 
Cheshire,  regard  these  inclosed  cones  as  hearing  organs.  They  sup- 
pose that  the  sound  waves  of  the  air  enter  the  pit,  as  into  an  ear 
cavity,  and  these  set  up  a  vibration  in  the  cone  which  stimulates  the 
attached  nerve  ending.  However,  the  appearance  of  one  of  these 
cones  would  suggest  that  it  is  too  stable  a  structure  to  be  affected 
by  sound  waves,  so  the  olfactory  theory  seems  much  more  probable. 

Finally,  Schiemenz  describes  the  most  specialized  of  all  the  anten- 
nal  sense  organs  as  a  closed  cavity  {Pt)  in  the  cuticle  {Cfl)  extend- 
ing into  the  holloAV  of  the  antenna  as  a  long,  curved,  tapering  sac. 
This  is  shown  at  F  of  figure  12.  A  nerve  {Xv)  enters  the  lower 
extremity  of  the  pouch,  expands  slightly  into  a  nucleated  ganglion 
cell  {Cl)^  and  then  extends  toward  the  top  as  a  delicate  spindle 
drawn  out  into  a  fine  tapering  point.  The  surface  covering  of  the 
pit  is  a  thin  layer  of  chitin  presenting  several  concentric  light  and 
dark  rings  surrounding  a  central  disc  {hr).  Sections  show  that  this 
appearance  of  rings  is  due  to  circular  thickenings  of  the  membrane, 
and  Schiemenz  points  out  that  the  central  disc  is  probably  a  modi- 
fied hair,  while  the  whole  structure  is  to  be  regarded  simply  as  a 
modification  of  a  tactile  organ  such  as  that  shown  at  D  with  the 
nerve-ending  and  its  ganglion  inclosed  in  a  sac.  These  organs  are 
most  abundant  on  the  antenna?  of  the  drones,  where  they  are  situ- 
ated, especially  on  the  under  surface,  so  close  together  that  but  little 
space  is  left  between  them  for  the  tactile  hairs,  while  in  the  workers 
and  (jiieens  they  are  farther  apart  and  are  interspaced  with  many 
tactile  hairs.  Hence,  whatcn-er  sense  they  accommodate  must  be 
much  more  highly  developed  in  the  males  than  in  the  females. 
Schiemenz  described  these  organs,  as  well  as  tlie  sunken  cones,  as 
organs  of  smell.  He  ascribed  only  the  senses  of  touch  and  smell  to 
the  antenna',  and  both  Cheshire  and  Cowan  concur  in  his  view  of  the 
closed  pits.  Arnhart  (  11)()(»),  h()we\(M',  argues  that  an  organ  of  smell 
must  be  oj)en  to  the  aii*  in  order  to  permit  the  ingress  of  odor  j)ar- 
ticles.  Such  an  organ  is  constituted  by  the  sunken  cones,  but  the 
closed  pits  lia\('  notliing  to  reconnnend  them  for  an  olfactory  func- 
tion. Arnhai-t  then  further  points  out  that  the  buried  sacs,  inclosing 
a  delicately  poised  nerve-ending  and  covered  by  an  external  tym- 
j)anuni.  have  all  the  mechanical  elements  of  an  organ  of  hearing. 
lie  linally  argues  that  bees  must  hear,  since  they  i)roduce  special 
soun<ls  such  ;is  the  i)ii)ing  of  the  queens,  and  that,  since  no  possible 


THE   HEAD   OF   THE   BEE   AND    ITS   APPENDAGES.  39 

organs  of  hearing  liavo  boon  discovered  on  any  other  part  of  the  body, 
some  of  the  antennal  sense  organs  nnist  be  anditory  in  function.  His 
conchision  from  these  premises  is,  of  course,  inevitable  that  the 
closed  sacs  on  the  antenna^  are  tlie  hearing  organs  of  the  bee.  What 
invalidates  the  argument,  however,  is  the  fact  that  no  one  has  yet 
])roduced  any  actual  evidence  that  bees  perceive  sound. 

The  following,  then,  may  be  stated  as  a  general  sunnnary  of  the 
evidence  concerning  the  antennal  senses  and  their  sense  organs  in 
the  bee:  (1)  The  antennae  are  highly  sensitive  to  touch  and  are  the 
seat  of  the  sense  of  smell.  (2)  They  are  covered  by  several  kinds 
of  minute  structures  which  are  modified  hairs  containing  special 
nerve-endings.  (3)  By  inference,  it  would  seem  certain  that  these 
are  the  sense  organs,  but  we  can  only  form  an  opinion,  based  npon 
their  structure,  as  to  which  are  tactile  and  which  olfactory.  (4)  One 
set  of  organs  does  not  appear  to  belong  to  either  of  these  categories 
and  their  structure  snggests  an  auditory  function,  but,  in  the  absence 
of  evidence  that  bees  hear,  the  purpose  of  these  organs  must  be  re- 
garded as  problematical. 

3.    THE   MANDIBLES  AND  THEIR  GLANDS. 

The  mandibles  (fig.  9  A,  Mel)  are  the  dark,  strongly  chitinous 
appendages  of  the  head,  commonly  called  the  jaws,  situated  at  each 
side  of  the  mouth,  anterior  to  the  base  of  the  proboscis.  In  all  in- 
sects with  biting  mouth  parts  the  jaws  work  sidewise,  each  being 
attached  to  the  head  by  an  anterior  and  a  posterior  articulation. 
They  can  thus  swing  in  and  out  on  a  longitudinal  axis  in  such  insects, 
as  the  bee,  that  carry  the  head  with  the  mouth  directed  downward, 
or  in  the  same  way  on  a  vertical  axis  in  those  that  carry  the  head 
with  the  mouth  forward. 

Both  mandibular  articulations  are  of  the  ball-and-socket  type, 
although  in  the  bee  the  socket  is  a  very  shallow  one,  the  anterior 
consisting  of  a  condyle  on  the  outer  angle  of  the  clypeus  fitting 
against  a  facet  on  the  mandible,  and  the  position  of  a  facet  on  the 
lower  edge  of  the  postgena  receiving  a  condyle  from  the  mandible. 
The  motion  of  the  mandible  is  thus  reduced  to  a  hinge- joint  move- 
ment, and,  on  this  account,  insects  can  only  bite  and  crush  their 
food ;  they  can  not  truly  chew  it,  since  their  jaws  are  incapable  of 
a  grinding  motion.  Each  mandible  is,  of  course,  as  pointed  out  in 
the  introduction,  really  suspended  from  the  head  by  a  continuous 
membrane  between  its  base  and  the  cranium,  being  simply  a  modified 
saclike  outgrowth  of  the  head  wall.  The  two  articulations  are  pro- 
ductions of  the  chitin  on  the  outside  of  this  membrane. 

Figure  9  A  shows  the  location  and  shape  of  the  mandibles  {Md) 
of  the  worker  as  seen  in  a  facial  view  of  the  head.     Figure  11  A 


40 


THE   ANATOMY    OF    THE    HONEY   BEE. 


RMcl 


shows  the  appearance  of  the  left  mandible  in  side  view,  Avhile  the 
right  one  is  shown  detached  from  the  head  in  figure  13  A.  The 
mandibles  differ  conspicuously  in  size  and  shape  in  the  three  forms 
of  the  bee  as  already  described  and  as  shown  in  figure  10  A.  B,  and  C. 
That  of  the  worker  is  hollowed  out  somewhat  on  the  distal  half  of 
its  inner  face  (fig.  13  A,  Md)  forming  a  spoon-shaped  organ,  the 
edge  of  which  is  smooth  and  rounded.  The  mandibles  of  both  the 
queen  (fig.  10  B)  and  the  drone  (C),  however,  are  pointed  at  the 
apex  and  have  a  conspicuous  subapical  notch.     Those  of  the  drone 

are  smaller  than  those  of 
either  form  of  the  female, 
but  appear  to  be  especially 
small  on  account  of  the 
great  size  of  the  drone's 
head.  The  mandible  of  the 
worker  is  undoubtedly  to 
be  regarded  as  the  special- 
ized form,  since  the  notched 
mandible  of  the  drone  and 
queen  is  of  the  ordinary 
Plymenopteran  type.  Both 
the  drone  and  the  queen 
are,  under  normal  circum- 
stances, fed  almost  entirely 
by  the  workers,  and  they 
l)robably  never  have  any 
use  for  their  jaws  as  feed- 
ing organs.  The  queen 
needs  her  large,  sharp- 
pointed  mandibles  for  bit- 
ing her  way  out  of  the 
thick  wax  cell  in  which 
she     is     reared,     but     the 


Fig.  13. — A,  right  mandible  of  worlcer,  anterior 
view,  with  extensor  and  flexor  muscles  (IJMcl 
and  li.Mcl)  and  mandibular  jilands  (iMdGl)  at- 
tached ;  B,  corresponding  view  of  mandible  of 
drone,  with  muscles  cut  off  a  short  distance  from 
their  bases. 


drcme,  on  the  other  hand, 
being  reared  in  an  ordinary  cell  resembling  that  of  a  worker,  except 
in  size,  is  easily  able  to  cut  through  the  thin  cell  cap  with  his  com- 
paratively weak  jaws.  The  workers,  however,  have  numerous  uses 
for  their  mandibles,  such  as  biting  through  the  cell  caps,  eating 
])ollen,  and  modeling  wax.  The  last  is  the  esi)ecial  function  of 
the  worker  mandible,  and  probably  it  is  to  acconnnodate  this  pur- 
pose that  it  has  acquired  its  specialized  spoonlike  shape. 

Each  iuaiidil)le  is  moved  by  tw^o  sets  of  muscles  within  the  head. 
The  outer  one  constitutes  the  cxtensoi'  muscle  (fig.  13  A,  PJMd)  and 
the  inner  the  fe.ror  ninsrlr   (RMcJ).     The  latter  is  the  stronger  of 


THE    HEAD    OF    THE    liEE    AN[)    ITS   APPENDAGES.  41 

the  two,  since  all  the  work  of  the  mandible  falls  upon  it,  the  extensoi- 
being  nsed  simply  to  open  the*  jaw.  While  these  muscles  have  their 
orio^ins  on  the  w^alls  of  the  head,  thev  are  not  inserted  directly  upon 
the  mandibles,  but  on  large  apodemes  (fig.  13  A,  EAp  and  AM//) 
attached  to  the  edges  of  the  mandible. 

A  gland  opens  at  the  inner  margin  of  each  mandible  between  the 
anterior  articulation  and  the  base  of  the  apodeme  of  the  flexor 
muscle  (fig.  13  A  and  B,  IMdGl).  In  the  worker  it  consists  of  a 
large  sac  covered  with  secreting  cells  lying  within  the  front  part  of 
the  head  between  the  clypeus  and  the  compound  eye  (fig.  10  A, 
IMdGl).  These  mandibular  glands  may  be  most  easily  studied  by 
removing  the  front  as  shown  in  figure  10  A,  B,  and  C.  In  order  to 
do  this,  pull  the  head  from  the  thorax  and  allow  the  prothoracic  legs, 
which  will  usually  come  off  with  the  head,  to  remain  attached  to  it. 
Next  melt  a  small  hole  in  the  bottom  of  a  paraffin  dish  w^itli  a  heated 
needle  and  fasten  the  head  face  upward  into  this,  the  attached  legs 
helping  to  anchor  the  head  in  the  paraffin.  Cover  the  specimen  with 
weak  alcohol  and  by  means  of  sharp  needles  remove  the  part  of  the 
front  on  either  side  between  the  clypeus  and  the  lower  half  of  the 
compound  eye  in  the  worker  and  drone  and  the  entire  front  of  the 
queen.  In  figure  10  the  whole  front  is  removed  in  all  three  forms  in 
order  to  expose  other  internal  parts  of  the  head. 

The  mandibular  gland  {IMdGl)  is  of  greatest  size  in  the  queen 
(fig.  10  B),  though  it  is  large  in  the  worker  (fig.  10  A  and  fig.  13  A), 
but  it  is  reduced  in  the  drone  (fig.  13  B)  to  a  very  small  oval  sac, 
which  is  hidden  by  another  gland  {2GI)  in  front  (fig.  10  C).  It  was 
first  described  by  Wolff  (1875)  as  an  olfactory  mucous  gland  {Riech- 
schleimdrusse)  and  was  supposed  by  him  to  secrete  a  liquid  which 
was  poured  upon  the  roof  of  the  mouth  in  order  to  keep  this  surface, 
on  which  Wolff'  thought  the  olfactory  organs  were  located,  in  a  moist 
condition  capable  of  absorbing  odor  particles.  There  is  absolutely 
no  evidence,  however,  of  the  presence  of  organs  of  smell  in  the  mouth, 
and  furthermore,  as  pointed  out  by  Schiemenz  (1883),  the  gland 
varies  in  the  three  forms  of  the  honey  bee  according  to  the  size  of  the 
mandible,  which  is  proportionately^  largest  in  the  queen  and  smallest 
in  the  drone.  Of  the  three,  we  should  ex])ect  the  drone  or  the  Avorker 
to  have  the  sense  of  smell  most  highly  developed,  and  hence,  even  if 
w^e  did  not  know  that  the  sense  of  smell  is  located  in  the  antennae, 
it  would  seem  more  reasonable  to  suppose  that  the  glands  of  the 
mandibles  are  connected  in  some  way  with  the  functions  of  these 
organs  themselves. 

The  mandibles,  as  already  stated,  are  used  for  eating  pollen  and  as 
tools  for  manipulating  and  modeling  wax.  Therefore,  according  to 
Arnhart  (1906),  since  the  queen  does  not  eat  raw  pollen,  the  product 


42 


THE  ANATOMY  OF  THE  HONEY  BEE. 


i)f  the  mandibular  glands  must  be  intended  for  softening  the  wax 
when  it  is  worked  in  the  jaws.  The  secretion  of  the  glands  is  said 
to  be  very  volatile  and  strong  smelling  and  to  have  an  acid  reaction. 
It  is  probably  entirely  possible  that  it  may  have  a  solvent  effect  upon 
the  wax,  or  even,  when  mixed  with  it.  change  somewhat  the  chemical 
composition  of  this  substance:  in  fact,  some  investigators  claim  that 
the  wax  of  the  comb  differs  chemically  from  that  freshly  taken  from 
the  Avax  plates.  Even  this  explanation,  however,  does  not  seem  en- 
tirely satisfactory,  for  the  only  occasions  on  which  the  queen  has  any- 
tliiiig  to  do  with  wax  is  when  she  gnaws  her  way  out  of  her  cell  after 
hatching  or  bites  her  way  into  the  cells  of  young  queens  in  order 
to  sting  them.  However,  these  occasional  uses  by  the  queen  of  her 
mandibles  appear  to  be  important  enough  to  maintain  the  large  size 
of  these  organs  in  the  queen,  and  it  may  be  reasonable  to  assume  that 
the  demand  upon  their  glands  is  likewise  a  large  one  when  it  does 

occur.  Yet  the  mandibles  of  the 
queen  are  toothed  and  sharp 
pointed,  which  should  provide  her 
with  sufficient  cutting  power  both 
to  emerge  from  her  own  cell  and  to 
enter  the  cells  of  other  queens,  and 
so,  on  the  Avhole,  the  opinion  of 
Schiemenz  that  the  secretion  of  the 
mandibular  glands  is  merely  sali- 
viwy  in  function  would  seem  to  be 
the  simplest  ex})lanation  and  the 
most  logical  one.  However,  an 
actual  test  should  certainly  be  made 
to  determine  whether  the  worker's 
manipulation  of  the  wax  with  her  mandibles  produces  any  change  in 
it,  and  to  discover  whether  the  (pieen  simply  bites  her  way  mechan- 
ically through  the  wall  of  the  cell  or  at  the  same  time  softens  the  wax 
by  a  secretion  from  her  mouth.  The  male  in  anv  case  has  little  use 
for  his  mandibles,  and  the  glands  are  so  small  that  they  must  certainly 
be  functionless. 

A  second  mandibular  gland  (tig.  14,  JMdGl)  is  present  in  the 
worker.  It  consists  of  a  delicate,  flattened,  racemose  mass  lying 
against  the  internal  face  of  the  wall  of  the  fossa  of  the  i)roboscis. 
whose  duct  opens  into  the  mouth  cavity  at  the  posterior  inner  edge 
of  the  mandible.  This  gland  was  first  described  by  Hordas  (1895)  as 
the  internal  m,andiJ)ylai'  (/hmd.  According  to  him,  it  corresponds 
with  a  similar  gland  in  the  Bombida'  (bumblebees)  and  in  the  Ves- 
])ida'  (yellow  jack(»ts)  and  to  the  maxillary  glands  of  other  Hy- 
iii('iiopl('i-a.      Notliing  is  known  of  its  secretion. 


2MdCl 

Fio.  14. — Internal  mandibular  srland 
(2M(1GI)  of  worker,  l.ving  against  inner 
wall  of  postgena  (Pgc)  and  openin.ir 
H)(t)  at  inner  edge  of  base  of  man- 
dible. 


THE   HEAD   OF   THE   BEE   AND   ITS   APPENDAGES.  43 

4.    THE    PROBOSCIS. 

The  conspicuous  oroup  of  month   appendages  in  the  honey  bee, 
forming  what  is  commonly  known  as  the  prohosch  (fig.  9  A,  Prh)^ 


Fig.  15. — Mouth  parts  of  the  worker:  A,  tip  of  glossa,  showing  labellum  {Lbl),  guard 
hairs  {Hr),  and  ventral  groove  (fc)  ;  B,  same,  from  above;  C,  small  piece  of  glossal 
rod  (r)  with  adjoining  parts  of  walls  {q)  of  glossal  canal  attached,  showing  ventral 
channel  (7)  guarded  by  rows  of  hairs.  D,  parts  forming  the  proboscis,  labium  in  middle 
and  maxillae  at  sides,  flattened  out,  ventral  view  ;  B,  cross  section  of  glossa  showing  its 
invaginated  channel  {Lum)  and  position  of  rod  (r)  along  its  dorsal  wall,  and  likewise 
position  of  channel  (7)  of  rod  along  median  line  within  the  glossal  channel;  F,  end  of 
mentum  (lit)  and  bases  of  ligula  (Lg)  and  labial  palpi  (LbPIp),  showing  opening 
of  salivary  duct  (SaWO),  dorsal  view;  G,  lateral  view  of  proboscis  showing  parts  on 
left  side;  H,  lateral  view  of  glossa  {Gls)  with  its  rod  (r)  torn  away  at  base  showing 
attachment  of  retractor  muscles   (2RMcl). 

by  means  of  which  the  bee  takes  up  liquid  food,  consists  of  what  cor- 
respond with  the  maxilhe  and  the  labium  of  insects  that  feed  on  solid 


44  THE  ANATOMY  OF  THE  HONEY  BEE. 

food  alone.  By  separating  the  parts  of  the  proboscis  a  little  (fig. 
J)  B)  it  will  be  seen  that,  while  there  are  hve  terminal  pieces  present, 
three  of  them  arise  from  one  median  basal  sclerite  (Mt),  the  U\o 
wider  lateral  appendages  (J/.r)  being  carried  each  by  a  separate  lat- 
eral basal  piece  (St).  The  median  group  constitutes  the  labium  and 
the  separate  lateral  parts  the  inaxillw. 

If  the  reader  will  now  turn  again  to  figure  3  C  (p.  IT).  Avhich  may 
represent  any  generalized  insect  labium,  and  compare  with  it  the 
drawing  of  the  bee  labium,  forming  the  median  series  of  parts  in  fig. 
15  D,  he  will  at  once  be  able  to  identify  the  parts  of  the  latter.  The 
principal  elongate  median  basal  plate  is  the  mentum  (Mt).  the  small 
triangular  plate  at  its  base  is  the  siihmentum  (Srnt),  and  the  two 
jointed  lateral  appendages  of  the  mentum  are  the  labial  jyalpl 
(LbPJp),  each  carried  by  a  basal  'palpiger  (Pig).  It  is  only  the  parts 
of  the  bee's  labium  that  lie  between  the  palpi  Avhich  are  actually 
different  from  those  in  the  generalized  diagram  where  they  consist 
of  the  four  lobes  of  the  ligula  {Gls  and  PgJ).  But  eyen  here  it  will 
be  seen  that  the  two  small  lobes  {Pgl)  in  the  bee's  labium,  partly  con- 
cealed within  the  bases  of  the  palpi,  correspond  with  the  paraglossa-. 
Hence  we  haye  only  the  long  median  appendage  to  account  for  and  it 
is  unquestionably  the  representatiye  of  the  glossa^  (Gls)  which  are 
here  fused  together  and  drawn  out  into  this  flexible  tonguelike  organ. 
In  fact,  a  comparison  with  the  mouth  parts  of  other  Hymeno])tera  in 
which  the  elements  are  much  less  modified  leayes  no  doubt  of  this 
being  the  true  interpretation  of  the  bee's  labium.  It  is  simply  an 
example  of  how  nature  constantly  prefers  to  modify  an  already  exist- 
ing part  to  serye  some  new  })uri)()se  rather  than  to  create  a  new  organ. 

If,  then,  we  bear  in  mind  that  the  slender  median  appendage  of 
the  bee's  labium  represents  the  gk)ssa^  of  other  insects,  we  may  for 
conyenience  call  it  the  ''  tcmgue,''  as  it  is  popuhirly  termed,  or,  since 
it  is  a  single  organ,  there  is  probably  no  grnnniiatical  objection  to 
calling  it  the  f/lossa.  The  word  "tongue,"  however,  to  use  it  prop- 
erly, shoidd  be  applied  to  the  true  lingua  or  Jn/popharyn.v  (fig.  3  C 
and  I),  Ilphij)  which  arises  fi'om  the  upjH'r  surface  of  the  labium. 
Many  of  the  older  entomologists,  adopting  the  notion  from  Kirby 
and  Spence,  who  defined  the  term  in  IS'iC).  regarded  the  glossa  of 
the  bee  as  the  hoiiiologiie  of  tlu'  liiigiiii  in  other  orders.  Even  Pack- 
ard in  his  Text-book  of  Kntoniology  calls  the  glossa  the  "hypo- 
pharynx."  dieshire  named  it  the  "ligula,"  and  his  mistake  has  been 
perpetuated  by  several  other  wi'iters  on  bee  anatomy,  including  Cook 
and  Cowan.  The  term  ligula  properly  includes  both  the  glossa  and 
the  paraglossa',  or  shonld  signify  the  basal  piece  from  which  these 
f(nir  lobes  arise  ( lig.  :'>  C.  Ar/),  so  that  it  can  not  be  applied  to  the 
tj^lossa  alone. 


THE    HEAT)    OF    THE    BEE    AND    ITS    API'ENDACIES.  45 

The  derivation  of  anatomical  names  counts  for  nothinij  in  their 
application — this  must  be  determined  by  scientific  usa«:e  and  priority. 
Thus,  glossa  is  the  Greek  word  for  '"tongue,"  but  it  was  first  applied 
in  entomology  to  the  median  lobes  of  the  labium ;  I'nujua  is  its  equiva- 
lent in  Latin  and  was  first  given  to  the  true  tongue  or  hypopharynx 
in  insects;  ligida  is  a  diminutive  derivative  from  *"  lingua '■  and  has 
come  to  be  applied  collectively  to  the  terminal  parts  of  the  labium 
beyond  the  mentum  but  not  including  the  palpi.  Hence,  all  these 
words  mean  the  same  thing  by  their  origins,  but  their  anatomical 
applications  should  be  carefully  distinguished.  In  this  paper  there- 
fore the  slender  median  appendage  [Gls)  of  the  labium  will  be 
called  the  glossa^  or,  for  convenience,  the  tongues  but  with  the  strict 
imderstanding  that  the  organ  in  question  is  not  the  true  tongue. 
This  latter  should  be  called  the  '*  hypopharynx,''  but,  as  will  be  shown 
later,  it  is  absent  in  the  bee. 

The  glossa  of  the  bee  (figs,  9  B;  11  A  and  B,  and  15  D,  F,  and  G, 
Gls)  is  covered  with  long  hairs  which  increase  in  length  toward  the 
end.  The  tip  is  formed  of  a  small  spoon-shaped  lobe,  the  lahelhim  or 
bouton  {Lhl)s  which  is  covered  by  short  delicate  processes  branched 
at  their  ends  (fig.  15  A  and  B.  LhJ).  The  long  hairs  of  the  glossa 
are  arranged  in  circles  and  the  transverse  rows  of  hair  bases  give 
the  tongue  a  miiltiarticulate  appearance.  Surrounding  the  dorsal 
side  of  the  base  of  the  labella  and  forming  two  short  subterminal 
rows  on  the  ventral  side  of  the  glossa  are  a  number  of  stiff,  out- 
wardly curved,  spinelike  hairs  (Hr).  These  hairs  have  been  de- 
scribed as  taste  organs,  but  their  appearance  would  suggest  that  they 
are  simply  j^rotective  spines  guarding  the  delicate  tip  of  the  tongue. 
Between  the  two  ventral  rows  of  these  spines  is  the  termination  of 
a  groove  (A,  k)  which  extends  along  the  midline  of  the  under  sur- 
face of  the  glossa  (D,  /.)  to  its  base  (fig.  9  B,  k).  The  cleft  of  this 
groove  is  covered  by  two  fringes  of  converging  hairs  whose  tips  are 
inclined  also  toAvard  the  tip  of  the  tongue. 

Let  us  now  return  to  a  study  of  figure  15  D.  The  series  of  lateral 
pieces  as  already  explained  are  the  maxillae.  A  comparison  with 
figure  3  B  representing  a  generalized  maxilla  will  show  that  these 
organs  in  the  bee  have  suffered  a  greater  modification  than  has  the 
labium,  but  the  parts  can  yet  be  quite  easily  made  out.  The  main 
basal  plate  (St)  is  the  combined  stipes,  suhgalea,  and  palpifer,  the 
basal  stalk  is  the  ccn^do  (Cd).  and  the  little  peglike  process  {MxPlp) 
at  the  otiter  end  of  the  stipes  is  the  greatly  redticed  maxillary  palpus. 
Hence,  we  have  left  only  the  terminal  blaclelike  lobe  {Mx)  to  account 
for,  and  it  is  evident  that  it  must  be  either  the  galea  or  the  lacinia 
(see  fig.  3  B,  Ga  and  Lc)  or  these  two  lobes  combined.  Here  again 
a  comparative  knowledge  of  the  mouth  parts  of  Hymenoptera  comes 


46  THE  ANATOMY  OF  THE  HONEY  BEE. 

to  our  aid  and  shows  clearly  that  the  part  in  question  is  the  outer 
lobe  or  galea^  for  the  inner  one  becomes  smaller  and  smaller  in  the 
higher  members  of  the  order  and  finally  disappears. 

The  base  of  the  submentum  is  connected  in  the  bee  with  the  upper 
ends  of  the  cardines  by  a  flexible,  widely  V-shaped  band,  the  lonnn 
(Lr).  The  posterior  angle  of  the  submentum  rests  in  the  apex  of  the 
lorum.  while  the  tips  of  the  loral  arms  are  movably  articulated  with 
the  distal  ends  of  the  cardines.  The  name  "  lora  "  Avas  given  to  this 
structure  by  Kirby  and  Spence.  but  "  lorum  "  is  more  correct,  since 
this  is  the  Latin  form  of  the  word  (meaning  a  thong  or  lash).  Some 
recent  entomologists  have  spoken  of  the  structure  as  consisting  of 
two  rods,  thus  making  the  Avord  do  duty  as  a  plural,  but  the  thing 
itself  is  all  one  piece.  Cheshire  and  some  others  have  incorrectly 
applied  the  name  to  the  submentum. 

The  lorum  is  peculiar  to  the  Hymenoptera,  and  the  reason  for  it 
is  clear  when  we  examine  the  attachments  of  the  parts  of  the  proboscis 
to  the  head.  As  already  stated,  the  maxilla^  and  labium  are  sus- 
pended in  a  large  cavity  on  the  back  of  the  head  which  may  be  called 
the  fossa  of  the  prohoscis  (fig.  9  B,  PrhFs).  The  maxilhr  are  articu- 
lated by  their  cardines  {Cd)  to  the  maxillary  suspensoria  (fig.  11 
A,  e)  at  the  upper  edges  of  the  side  walls  of  the  fossa.  The  labium, 
on  the  other  hand,  is  not  attached  to  the  solid  walls  of  the  cranium 
but  is  suspended  in  the  membranous  floor  of  the  fossa.  This  is  to 
afford  it  freedom  of  movement  during  feeding,  but.  in  order  to 
give  it  more  substantial  support  and  to  make  the  regulation  of  its 
motions  possible,  the  submentum  is  slung  to  the  ends  of  the  cardines 
by  the  lorum. 

The  terminal  lobes  of  the  labium  and  maxilla*  when  not  in  use 
are  ordinarily  folded  down  beneath  the  head  against  the  mentum 
and  stipites  (fig.  19).  When,  however,  the  bee  wishes  to  imbibe  a 
thick  liquid  such  as  honey  or  sirup  in  large  quantity,  these  parts  are 
straightened  out  and  held  close  together  so  as  to  form  a  tube  between 
them  leading  into  the  mouth,  the  terminal  joints  of  the  labial  palpi 
alone  diverging  from  the  rest   (fig.  11  A). 

The  action  of  the  mouth  parts  while  feeding  may  be  observed  quite 
easily  if  some  bees  are  given  a  small  amount  of  honey  and  then 
watched  through  a  lens  while  they  are  eating.  A  most  convenient 
method  is  to  j)ut  a  few  workers  in  a  small  screen-covered  cage,  such 
as  are  used  for  (lueen  nurseries,  spread  a  small  drop  of  honey  on  the 
wire,  and  then  i)lace  the  cage  under  a  simple  niicroscoix^  It  will  be 
seen  that  the  maxilhe  are  held  almost  stationary  but  that  the  base 
of  the  labium  slides  back  and  forth  between  the  maxillary  bases 
with  a  very  regular  to-and-fro  movement  as  if  the  honey  were  being 
either  ])umpe(l  or  sucked  up  into  tlie  month.  It  is  probable  that  there 
i^  a  mucking  force  exerted  by  the  pharynx  i^i\<^.  11  13,  Phy)  but  not 


THE    HEAD    OF    THE    BEE    AND    ITS    APPENDAGES.  47 

by  the  honey  stomach  (fig.  44,  //aS'),  which  laller,  as  Cheshire  re- 
marks, could  no  more  suck  honey  through  the  (rsophagus  than  a 
balloon  could  suck  gas  from  a  pipe.  The  liquid  undoubtedly  runs 
up  the  temporary  tube  between  tlie  blades  of  the  mouth  parts  first 
by  cajDillary  attraction,  but  it  must  be  greatly  assisted  along  its  way 
to  the  mouth  by  the  retraction  of  the  labium.  The  load  brought  up 
when  this  is  pulled  back  is  then  sucked  into  the  mouth  by  the 
pharynx  while  the  labium  immediately  goes  out  again  after  more. 
It  acts  thus  as  a  sort  of  mechanical  feeder  and  this  function  is  prob- 
ably derived  from  the  lapping  motion  of  the  under  lip  in  wasps  and 
hornets. 

The  mentum  (fig.  15  D  and  G,  Mt)  is  hinged  freely  upon  the 
submentum  (Smt),  the  latter,  as  already  described,  is  set  into  the 
socketlike  angle  of  the  lorum,  while,  finally,  the  arms  of  the  lorum 
are  articulated  to  the  distal  ends  of  the  cardines  of  the  maxillae. 
Xow,  when  the  labium  is  retracted  by  means  of  muscles  attached  to 
the  mentum.  the  submentum  turns  in  the  loral  socket  and  assumes  a 
position  at  right  angles  to  the  mentum  while  the  lorum  itself  turns 
somewhat  on  its  articulations  with  the  cardines.  This  great  freedom 
of  motion  is  permitted  by  the  loose  membrane  of  the  fossa  in  which 
both  the  maxilla^  and  the  labium  are  suspended. 

The  observer,  however,  can  not  fail  to  note  that  beside  this  motion 
of  the  enti^'e  labium  the  tongue  itself,  or  glossa  (GIs),  performs  a 
conspicuous  independent  movement  of  its  own.  It  is  by  far  the  most 
active  member  of  the  mouth  parts  during  feeding,  being  actively 
thrust  out  and  retracted  while  its  tip  is  constantly  moved  about  in 
a  way  suggestive  of  its  being  delicately  perceptive  of  taste  or  touch 
or  perhaps  to  both  of  these  senses.  So  great  is  the  retractile  power 
of  the  tongue  that  its  tip,  which  normally  extends  far  beyond  the  end 
segments  of  the  labial  palpi,  can  be  drawn  back  entirely  within  the 
latter.  This  contractile  activity  appears  at  first  sight  to  be  due  to 
elasticity,  but  a  closer  examination  will  show  that  the  entire  ligula, 
i.  e.,  the  paraglossse  (Pgl)  as  well  as  the  glossa  (GIs),  moves  back 
and  forth  and  that  the  action  is  due  to  a  retraction  of  the  base  of  the 
ligula  (fig.  15  F,  Lg)  into  the  anterior  end  of  the  mentum  (Mt). 
The  ligula  is  supported  on  a  membranous  cone  at  the  end  of  the 
mentum  whose  walls  are  strengthened  by  three  thin  chitinous  plates, 
two  above  (F,  p)  and  one  below  (D,  o).  By  the  contraction  of 
nuiscles  situated  within  the  mentum  (fig.  16,  iRMcJ)  and  inserted 
upon  the  base  of  the  ligula  the  latter  is  pulled  into  the  end  of  this 
cone  whose  walls,  including  the  chitinous  plates,  simply  turn  inward. 

But  the  tongue  does  possess  also  a  contractile  power  of  its  own  by 
means  of  which  it  actually  shortens  its  length.  A  flexible  rod  arising 
from  the  median  ventral  supporting  plate  (fig.  15  D,  o)  of  the  ligula 
extends  throughout  its  length.     The  base  of  this  rod  is  curved  down- 


48  THE  ANATOMY  OF  THE  HONEY  BEE. 

ward  and  has  two  muscles  attached  to  it.  This  is  shown  by  figure 
15  H,  where  the  rod  (r)  is  torn  from  the  glossa  {Gls)  basally  so  as 
to  show  the  muscles  {2RMcl)  inserted  upon  it  and  its  connection 
with  the  plate  {o).  By  the  contraction  of  the  muscles  the  rod  bends 
at  its  base  and  is  drawn  back  into  the  mentum.  The  glossa  thus 
shortens  and  becomes  bushy  just  as  does  a  squirrel's  tail  when  one 
attempts  to  pull  the  bone  out  of  its  base. 

The  protrusion  of  the  parts  is  due  to  the  pressure  of  blood  driven 
into  the  ligula  from  the  mentum,  while  probably  the  glossa  extends 
also  by  the  straightening  of  its  rod  as  the  muscles  relax.  Wolff 
described  a  protractor  muscle  at  the  base  of  the  ligula.  The  rod  of 
the  tongue  is  certainly  not  in  itself  contractile,  as  supposed  by 
Cheshire,  who  looked  for  evidence  of  muscular  striation  in  it.  It  has 
mostly  a  transparent  and  cartilaginous  appearance,  but  is  presumably 
chitinous. 

The  mouth  parts,  their  action  in  feeding,  and  the  muscular  mech- 
anism by  which  the}"  are  moved  have  been  elaborately  described 
and  illustrated  by  Wolff  (1875)  in  his  monograph  on  the  organs  of 
smell  in  bees.  Most  unfortunately,  however,  Wolff's  paper  was 
written  to  show  that  the  seat  of  the  sense  of  smell  is  in  the  mouth, 
a  most  erroneous  notion,  and  the  title  of  his  paper  based  on  this 
notion  has  caused  little  attention  to  be  paid  to  this  work  on  the  mouth 
parts  of  the  bee,  which  is  one  of  the  best  anatomical  treatises  ever 
produced  on  the  mouth  jjarts  of  any  insect. 

It  still  remains  for  us  to  describe  the  details  of  the  glossa  and  its 
particular  function  in  feeding.  The  tongue  is  not  a  solid  appendage 
nor  yet  is  it  truly  tubular.  A  compromise  is  effected  by  the  longi- 
tudinal groove  (fig.  15  A  and  D,  /.)  on  its  ventral  surface  which 
expands  within  the  tongue  into  a  large  cavity  occupying  half  of  its 
interior  (E,  Lum).  The  glossal  rod  (r),  which  has  already  been 
mentioned,  lies  in  the  dorsal  wall  of  this  channel  and  is,  hence, 
really  not  an  internal  but  an  external  structure.  The  rod  is  itself 
grooved  along  its  entire  ventral  length  (E,  /)  and  this  groove  again 
is  converted  into  a  tube  by  two  rows  of  short  hairs  which  converge 
from  its  margins.  The  lii)s  of  the  ventral  groove  of  the  glossa  are 
so  deeply  infolded  that  its  cavity  is  almost  divided  along  the  midline. 
Hence,  the  glossa  might  be  described  as  containing  three  channels — 
a  small  niedinn  dorsal  one  (7)  and  two  large  latero-ventral  ones 
{Luni). 

The  glossal  i-od  (fig.  15  C,  r)  is  very  flexible  but  not  contractile,  as 
already  stated,  and  is  mostly  clear  and  cartilaginous  in  ai)pearance, 
its  ventral  groove  {!)  alone  being  lined  by  a  deposit  of  (hirk  chitin 
(lig.  15  C  and  Vj).  I(s  shape  in  section  is  sufficiently  shown  by  the 
figures.  The  walls  of  the  hii-ge  channels  of  the  proboscis  consist  of 
a  delicate  membrane   [C  and   E.  q)   covered  with  very  small  hairs. 


THE    HEAD    OF    THE    BEE    AND    ITS   APPENDAGES.  49 

The  entire  ventral  cavity  {Lutn)  w  illi  llie  rod  (/-)  can  be  evaginated 
through  the  ventral  cleft  {k)  by  blood  pressure  from  within.  As 
Cheshire  points  out,  this  permits  of  the  channels  being  cleaned  in 
case  of  clogging  by  pollen  or  any  foreign  matter. 

It  is  supposed  that  these  glossal  tubes  are  of  especial  service  to  the 
bee  by  enabling  it  to  take  up  the  smallest  drops  of  nectar — quantities 
that  would  be  lost  in  the  clumsy  tube  formed  between  the  parts  of 
the  Jabium  and  the  maxilla?.  The  suction  must  be  in  large  part 
capillary  attraction,  but  here  again  the  shortening  of  the  glossa  by 
the  retraction  of  its  rod  must  squeeze  the  contained  nectar  out  of  the 
upper  ends  of  the  channels  where  it  is  received  upon  the  ventral  flaps 
of  the  paraglossse  (fig.  15  F,  Pgl)^  from  which  it  runs  around  the 
base  of  the  tongue  {Gls)  within  the  paraglosste  to  the  dorsal  side  of 
the  mentum  {Mt)  and  so  on  to  the  mouth. 

The  maxillae  and  labium  of  both  the  queen  and  the  drone  (fig.  11 
B)  are  smaller  and  weaker  than  those  of  the  worker,  and  neither  of 
these  two  forms  is  capable  of  feeding  itself  to  any  extent.  If  a 
hungry  queen  be  given  some  honey  she  attempts  to  eat  it  and  does 
imbibe  a  small  quantity,  but  at  the  same  time  she  gets  it  veiy  much 
smeared  over  her  head  and  thorax. 

The  mouth  is  hard  to  define  in  insects;  practically  it  is  the  space 
surrounded  by  the  bases  of  the  mouth  parts,  but  strictly  speaking  it 
is  the  anterior  opening  of  the  alimentary  canal  situated  behind  the 
bases  of  the  mouth  parts  (fig.  19,  Mth).  Yet  the  enlargement  of  the 
alimentar}^  canal  (Phy)  immediately  following  this  opening  is  never 
spoken  of  as  the  mouth  cavity  but  is  called  the  pharynx.  On  the 
other  hand  the  so-called  epipharynx  (Epluj)  and  hypopharynx 
(absent  in  the  bee)  are  located  in  front  of  this  opening  and  are  con- 
sequently not  in  the  pharynx  at  all,  the  former  being  attached  to  the 
under  surface  of  the  labrum  and  clypeus,  while  the  latter  is  situated 
on  the  upper  surface  of  the  base  of  the  labium.  These  and  numerous 
other  inconsistencies  in  the  nomenclature  of  insect  morphology  have 
to  be  endured  because  the  parts  were  originally  named  for  descrip- 
tive purposes  by  entomologists  who  were  not  familiar  with  scientific 
anatom}^  In  this  paper  the  term  mouth  will  be  applied  to  the  true 
oral  opening  (fig.  19,  Mth).  The  space  in  front  of  it  between  the 
bases  of  the  mouth  parts  maj^  be  called  the  preoral  cavity. 

The  duct  of  the  salivary  glands  of  insects  in  general  opens  upon  the 
base  of  the  labium  in  front  of  the  hypopharynx.  In  the  honey  bee 
the  salivary  opening  is  on  the  dorsal  side  of  the  base  of  the  ligula 
between  the  paraglossse  (fig.  15  F^  SalDO).  This  alone  would  show 
that  the  glossa  is  not  the  hypopharynx  of  the  bee,  as  many  authors 
have  supposed,  for  otherwise  the  opening  of  the  salivary  duct  should 
be  ventrad  to  the  base  of  the  glossa.     In  fact,  this  makes  it  clear  that 

22181— Xo.  18—10 4 


50  THE  AXATOMY  OF  THE  HOXEY  BEE. 

the  bee  does  not  possess  a  hypopharynx.  Theit'  is.  hoAvever,  a  con- 
spicuous chitinous  plate  located  on  the  anterior  part  of  the  floor  of  the 
pharynx  (fig.  19,  s)  having  two  terminal  points  hanging  downward 
over  the  lower  lip  of  the  oral  aperture,  but,  although  this  plate  is  truly 
hypopharyngeal  in  position,  it  is  not  the  homologue  of  the  organ 
called  the  hypopharynx  in  other  insects.  It  is  variously  developed 
in  all  Hymenoptera,  being  simply  a  chitinization  of  the  floor  of  the 
pharynx,  and  should  be  called  the  phcD-yngeal  plate  {Schlundhein  of 
AVolff).  It  will  be  more  fully  described  in  connection  with  the  ali- 
mentary canal.  If  a  hypopharynx  were  present  it  should  be  situated 
on  the  upper  side  of  the  labium  (see  fig.  3  D,  Ilphy)  but  there  is  here 
present  onh^  a  plain  arched  membranous  surface  in  the  honey  bee 
and  other  typical  Hymenoptera. 

The  external  location  of  the  salivary  opening  enables  the  saliva 
to  be  mixed  with  the  food  before  the  latter  enters  the  mouth.  This 
is  necessary  in  insects  since  the  jaws  are  also  on  the  outside  of  the 

GIs  ^\        \ \. 


Lum 


Fk;.  10. — Median  section  through  distal  half  of  lueutum  (Mi)  and  base  of  ligula  {L(j\ 
of  worker,  showing  opening  of  salivarj'  duct  (t^alDO),  and  muscles  connected  with 
ligula  and  the  "salivary  syringe"   (t). 

mouth,  and  whatever  chewing  or  crushing  the  food  receives  from 
them  is  consequently  done  in  the  preoral  cavity. 

In  some  insects  the  saliva  is  used  for  other  purposes  than  diges- 
tion. For  example,  tl)e  saliva  of  some  prechiceous  insects  with  i)ierc- 
iiig  mouth  parts  belonging  to  the  order  Hemiptera  is  poisonous,  and 
when  one  of  these  insects  "  bites,"  the  saliva  is  injected  into  the 
wound  by  a  special  pump.  The  bite  of  the  mosquito  is  made  painful 
likewise  by  an  irritant  secretion  from  a  part  of  the  salivary  glands. 
Bees  appear  to  have  the  power  of  letting  their  saliva  run  down  the 
tongue  when  necessary  to  dissolve  a  hard  substance  like  sugar  and 
render  it  capable  of  being  taken  up  in  solution,  for  they  do  not  eat 
sugar  witli  their  mandibles.  Moreover,  there  is  even  a  sort  of  })ump 
or  so-called  '' salivarv  svrini^e  "  at  the  termination  of  the  salivarv 
duct  in  the  ligula.  by  means  of  which  (he  secretion  can  be  foi'cibly 
ejected  from  the  opening. 

The  salivary  opening  on  the  base  of  the  ligula  (lig.  15  F,  SalDO) 
leads  into  a  deej)  transverse  ])it  with  collapsible  cartilage-like  walls 
having  its  deepest   part   turned   lioi'izontally  towai'd   the  base  of  the 


THE    HEAD   OF    THE    BEE   AND    ITS   APPENDAGES. 


51 


labium  (fig.  10,  t).  The  salivary  duct  {Sail))  bends  downward  in 
the  anterior  part  of  the  mentuni  {Mt)  and  opens  into  the  posterior 
end  of  the  pit  {t).  When  the  retractor  muscles  {iRMcl)  of  the 
ligula  pull  the  latter  back  into  the  mentum  the  lips  of  the  salivary 
pit  must  necessarily  be  closed.  The  simultaneous  contraction  of  the 
elevator  muscle  {ii)  attached  to  the  roof  of  the  horizontal  part  of  the 
pit  must  expand  the  latter  and  suck  the  saliva  from  the  salivary  duct. 
AVhen,  finally,  these  muscles  relax  and  the  ligula  is  driven  out  by 
blood  pressure  in  the  mentum,  probably  produced  in  part  by  the 
contraction  of  its  dorsal  transverse  muscles  (TJIcl),  the  saliva  in 
the  temporarily  formed  bulb  nuist  be  squirted  out  upon  the  base  of 
the  tongue.  Wolff  (1875)  calls  each  dorsal  longitudinal  muscle  of 
the  mentum  {iRMcl) — the  two  inserted  upon  the  basal  hooks  (n)  of 
the  glossa  (fig.  15  H  and  fig.  10) — the  retractor  lingua'  longus.  The 
large  ventral  retractor  muscle  of  each  side  {2RMcl)  he  calls  the 
retractor  linguce  biceps  since  its  anterior  end  divides  into  two  parts, 
one  of  which  is  inserted  by  a  tendonous  prolongation  upon  the  base 
of  the  glossal  rod  (fig.  15  H  and  fig.  10,  r)  and  the  other  upon  the 
base  of  the  ligula.  The  use  of  the  word  "  lingua  "  in  these  names  is 
objectionable  because,  as  already*  explained  (page  45),  the  lingua  is 
properly  the  true  tongue  or  hypopharynx.  "  Ligulse  "  should  be  sub- 
stituted for  *'  linguae.'-  The  dilator  muscle  (fig.  10,  u)  of  the  salivary 
pit  {t)  is  termed  the  protractor  linguce  by  Wolff  because,  as  he  sup- 
poses, when  the  ligula  is  pulled  back  into  the  mentum  the  position 
of  this  muscle  is  reversed,  so  that  a  contraction  of  its  fibers  would 
heljD  to  evert  the  ligula. 

The  glands  that  furnish  the  saliva  lie  within  the  head  and  the 
thorax  and  will  be  described  later  in  connection  with  the  alimentary 
canal  and  the  process  of  digestion. 


Fig.  1- 


-Epipharynx  {Ephij)   and  labrum   (Lw)   of  worker:  A,  ventral  view;  B, 
anterior  view. 


D.    THE  EPIPHARYNX. 


The  epipharynx  of  insects  in  general  may  be  described  as  a  dorsal 
tongue,  it  being  a  median  lobe  developed  on  the  roof  of  the  preoral 
cavity  from  the  Under  surface  of  the  clypeus  or  labrum  and  situated 
opposite  the  hypopharynx. 


52 


THE   ANATOMY    OF    THE    HONEY    BEE. 


The  epipharynx  of  the  bee  is  a  large  three-lobed  appendage  de- 
pending from  the  roof  of  the  preoral  cavity  just  in  front  of  the  mouth 
(fig.  19,  Ephy).  Seen  from  below  it  is  triangular  (fig.  17  A)  Avith 
the  apex  forward.  Its  median  lobe  has  the  form  of  a 
high,  vertical,  keel-like  plate,  Avhile  the  lateral  lobes 
are  rounded  but  have  prominent  elevated  edges  con- 
verging toward  the  front  of  the  keel.  The  appearance 
in  anterior  view  is  shown  by  figure  IT  B.  Situated 
on  the  posterior  parts  of  the  lateral  lobes  are  a  num- 
ber of  sense  organs,  each  consisting  of  a  small  cone 
with  a  pit  in  the  summit  bearing  a  small  hair  (fig.  18). 
These  are  regarded  as  organs  of  taste. 
Wolff  (1875)  made  a  most  thorough  study  of  the  epiphar3aix, 
which  he  called  the  "palate  sail"  {Gaumensegel)  on  account  of  the 
high  median  crest.  His  drawing  is  the  standard  illustration  of  the 
organ  found  in  nearly  all  books  on  the  anatomy  of  the  honey  bee 


\ 

?^^ 

B 

^ 

V, 

'^ 

# 

^ 

Fig. 

18.- 

-Sense 

organs, 

,     prob- 

ably    of 

taste, 

f  r 

o  m 

e  p  i  - 

ph{ 

irynx 

Int  BW         SalD      ^ 


ri<;.   lit.      Median  lonKitiidinal  section  of  li(>:i(l  of  worker,  but  with  (Mitire  labium  attaclied, 
sbowJn;^  int(>rnal  or^^ans  c^xcept   niuseles  and  brain. 

and  in  most  works  on  general  insect  anatomy  and  the  sense  organs. 
\\'()lir,  however,  regarded  the  sensory  cones  as  having  an  olfactory 
function,  nnd  lliis  led  liiiii  lo  erroneous  conclusions  regarding  the 
riinclions  of  several  oilier  organs.  V\)v  (example,  he  thought  that 
Ihc   mandibular  glands   poured    a    \\i[\\\(\    upon   the   surface   of  the 


THE    THORAX   AND   ITS    APl'KNDAGEo. 


53 


epipharynx  which  kept 
particles,  while  he  ex- 
plained the  inhalation 
of  the  latter  into  the 
preoral  cavity  as 
brought  about  through 
the  contraction  of  the 
air  sacs  situated  about 
the  mouth.  Wolff's 
anatomical  researches 
are  without  doubt 
some  of  the  best  ever 
made  on  the  bee,  and 
it  is  due  to  his  mis- 
taken idea  of  the  loca- 
tion of  the  sense  of 
smell,  which,  as  al- 
ready explained,  is  on 
the  antenna^,  that  we 
have  received  from 
him  a  most  excellent 
account  and  detailed 
drawings  not  only  of 
the  epipharynx  but  of 
the  mandibular  glands, 
the  mouth  parts,  the 
salivary  "  pump,''  and 
the  respiratory  organs. 

IV.  THE  THORAX  AND 
ITS  APPENDAGES. 

1.     THE    STRUCTURE    OF 
THE   THORAX. 


-VT 


The  apparent  thorax 
of  the  bee  (fig.  20, 
T^-IT,  and  fig.  21) 
and  of  most  other 
Hymenoptera  is  not 
exactly  the  equivalent 
of  the  thorax  in  other 
insects.  The  middle 
division  of  the  body, 
so  conspicuous  in  this 
order,  consists  not  only  of  the  three  leg-bearing  segments,  which  alone 


Fig. 


20. — Dorsal  view  of  ventral  walls  and  internal  skele- 
ton of  body  of  worker. 


54 


THE   ANATOMY   OF   THE   HONEY   BEE. 


constitute  the  thorax  of  all  other  insects,  but  also  of  the  first  ab- 
dominal segment.  The  conspicuous  necklike  constriction  posterior  to 
the  base  of  the  hind  legs  (fig.  21,  Pel)  is,  therefore,  between  the  first 
and  the  second  abdominal  segments  (fig.  1,  IT  and  I  IT). 

The  thorax  of  the  honey  bee  at  first  sight  looks  entirely  different 
in  structure  from  that  of  all  other  insects  except  related  Hymenoptera, 
in  the  higher  families  of  which  group  it  is  more  highly  modified  than 
in  any  other  order  of  the  whole  series  of  insects.  'Wlien,  however,  we 
examine  the  thorax  of  one  of  the  lowest  members  of  the  Hymenop- 
tera, such  as  a  sawfly,  we  are  surprised  to  find  that,  in  each  segment, 
the  structure  agrees  very  closely  with  our  ideal  diagram  of  a  general- 

ized  thoracic 
1-2  segment  (fig.  -i). 

The  three  seg- 
ments are  per- 
fectly distinct, 
and  the  first 
abdominal  seg- 
ment, while  it 
may  be  clearly 
separated  from 
the  rest  of  the 
abdomen,  is  not 
fused  into  the 
thorax  so  as  to 
appear  to  be  a 
part  of  it.  If, 
now,  we  exam- 
ine representa- 
tives of  several 
families  inter- 
mediate between 
the  sawflies  and 

the  bees,  the  line  of  specialization  that  has  produced  the  bee  thorax 
becomes  perfectly  evident.  The  principal  features  in  these  modifi- 
cations are  the  following: 

(1)  The  lateral  and  ventral  parts  of  the  prothorax  (figs.  20  and  21, 
A'/^S'i  fuul  aS'i)  are  suspended  loosely  in  a  large  membranous  area 
wliich  is  continuous  anteriorly  as  the  neck.  They  thus  form  a  sort 
of  suspensorium  for  the  front  legs,  which  appears  detached  from  the 
rest  of  the  thorax.  (2)  The  protergum  (7',)  is  solidly  attached  to 
tlic  anterior  edge  of  the  mesothorax  and  its  lateral  parts  extend 
downward  till  they  meet  on  the  venter  behind  the  prosternum  (figs. 
20  and  21).  (:i)  The  jiostnotum  (postscutelhun)  of  the  mesothorax 
(figs.  22.  I*X :  2:i  A,  PX.)  is  (Mitirely  in\aginated  into  the  cavity  of 
the  tliorax  and  is  reduced  to  the  form  of  two  lateral  arms  of  the  large 


ri<;.  1*1. — Thorax  of  worker,  left  side,  with  intersegmental  lines 
somewhat  exagj^erated.  showinj;  prothorax  (7'i,  Eps^,  CXi), 
mesothorax  (Tn,  Epsj,  Eptii-2.  ^'l•,  Cx.2),  metathorax  (T3.  Pla, 
pin,  Cxs)   and  propodeura  or  first  abdominal  segment    (IT). 


THE    'I'llORAX    AND    IIS    API'KNDACJKS.  55 

internal  postpliru^ina  (Pj>h)  wliicli  \\\\>  no  nicdian  tergal  connection 
at  all.  (4)  The  nietaterguni  (figs,  lil  and  ji)i  A,  7'.,)  consists  of  a 
single  narrow  plate.  (5)  The  nietaijlenrnni  (fig.  21,  Pl.,^  and  j)L) 
shows  no  trace  of  a  division  into  episternuni  and  epinieruni,  but  is 
divided  into  an  upper  (P/^.,)  and  a  lower  (pl-^)  pleural  plate.  (G) 
The  first  abdominal  terguni  (fig.  21,  IT)  is  solidly  attached  to  the 
nietathorax  and  forms  an  intimate  part  of  the  thoracic  mass. 

We  shall  now  proceed  with  a  more  detailed  account  of  the  thorax, 
and  the  reader  should  occasionally  turn  back  to  figure  4  (p.  19)  in 
order  to  keep  clearl}-  in  mind  the  parts  that  make  up  a  generalized 
thoracic  segment. 

The  parts  of  the  prothorax  are  so  separated  from  each  other  that 
they  appear  to  l)elong  to  ditl'erent  segment,s.  The  protergum  (fig.  21. 
y'l)  forms  a  collar  completely  encircling  the  front  of  the  mesothorax. 
On  each  side  a  large  lobe  {ic)  projects  posteriorly  as  far  as  the  base 
of  the  front  wing  and  constitutes  a  protective  shield  over  the  first 
thoracic  spiracle.  The  tergum  presents  a  median  transverse  groove, 
dividing  it  into  an  anterior  and  a  posterior  part,  which  parts  may 
])e  called  the  scutmn  (fig.  23  A,  T^,  Set)  and  scutellum  {Scl).  The 
proplenrum  (figs.  20,  21,  Eps^)  consists  of  a  large  plate  presenting 
both  a  lateral  surface  (fig.  21)  and  a  ventral  surface  (fig.  20).  On 
account  of  the  position  of  the  coxal  articulation  (fig.  21)  this  plate 
would  seem  to  be  the  anterior  pleural  plate  alone  (see  fig.  4),  wdiich 
IS  the  episternum.  In  some  Hymenoptera  the  epimerum  is  repre- 
sented by  a  very  small  plate  on  the  rear  edge  of  the  episternum. 
The  anterior  ends  of  the  two  episterna  form  knobs  which  loosely 
articulate  with  the  occipital  region  of  the  head  (figs.  11  B,  20,  and 
21).  Lying  just  ventrad  of  each  is  a  slender  cervical  sclerite  (fig.  21, 
mi).  The  prosternum  (aS'^)  is  shown  by  figure  20.  It  carries  a  large 
cntosternum  {Fii^)^  forming  a  bridge  over  the  nervous  system  behind 
the  prothoracic  ganglion  (fig.  52). 

The  mesotergum,  as  seen  in  its  natural  2:)Osition  (fig.  21,  T.,),  consists 
of  a  large  anterior  scutum  (Set.,)  and  of  a  smaller  but  very  prominent 
posterior  scutellum  (Scl^),  separated  by  a  very  distinct  suture  (r). 
The  scutellum  has  two  latero-anterior  areas  partially  separated  from 
the  median  area  by  suturas.  AMien  the  mesotergum  is  detached  from 
the  rest  of  the  thorax  (fig.  22)  it  is  discovered  that  there  is  attached 
laterally  to  the  scutellum  a  large  posterior  internal  part,  which  does 
not  show  on  the  surface  at  all.  This  is  the  representative  of  the 
postscutellum  (PhcI)  and  its  phragma  (Pph)  constituting  the  post- 
notum  (PX)  of  our  diagrammatic  segment  (fig.  4).  The  proof  of 
this,  again,  is  to  be  derived -from  a  study  of  the  lower  Hymenopteran 
families.  In  some  of  the  horntails  (Siricidne)  the  postnotum  or 
postscutellum  is  a  prominent  plate  on  the  surface  of  the  dorsum  be- 
hind the  scutellum.     In  Sirex  (Siricida?)  this  plate  is  sunken  below 


56 


THE    AXATCnrY    OF    THE    HOXEY    BEE. 


the  general  surface  and  mostly  concealed  between  the  mesothorax 
and  the  nietathorax.  In  higher  families  such  as  the  Pompilidae  the 
postnotum  of  the  mesotergum  is  entirely  concealed  by  inyagination, 
but  it  still  carries  a  yery  large  phragma.  AMien,  now,  we  come  to 
the  highest  members  of  the  order  we  find  that  the  median  part  of  the 
postnotum  in  the  mesothorax  is  gone  entirely  and  that  it  is  repre- 
sented only  by  the  lateral  arms  (figs.  22,  PX ;  23  A,  PX.)  carrying 
the  large,  purely  internal  postphragma  (Pph). 

The  mesopleurum  is  large  and  consists  principally  of  the  episternum 
(fig.  21,  Ep.s.,),  which,  howeyer,  is  continuoush^  fused  with  the  meso- 
sternum  (figs.  20  and  21,  S.^).  The  pleural  suture  (fig.  21,  PS,)  is 
short  and  sinuous  and  does  not  reach  more  than  half  way  from  the 
wing  process  to  the  base  of  the  middle  leg.  The  epimerum  is  reduced 
to  a  small  double  j^late  lying  aboye  the  episternum  and  posterior  to 
the  wing  process  (figs.  21,  Ep?n.,^  and  24  A,  Epm  and  Epm).     The 

pleural  ridge  (fig.  24  B,  PR) 
is  weak,  but  the  wing  process 
(irP)  is  well  braced  by  a  num- 
ber of  accessory  internal  ridges. 
One  preparapterum  {2P)  and 
one  postparapterum  {3P)  are 
present.  L^'ing  behind  the 
postparapterum  is  another 
larger  sclerite  (fig.  2-1  A  and 
B,  pn).  whose  anterior  end  is 

Fig.    22.— Lateral     view     of     mesotergum     of      articulated    to    the    edge    of    the 
worker,  removed  from  the  rest  of  thorax  to  .  i        i  • 

show   large   internal   postscuteiium    (post-     epimerum  and  whose  j^josterior 
notum,  py)   and  its  phragma   (Pph)  not     tapering    end    is    loosely    asso- 

visible  normallv  in  the  bee  from  rxterior.  .  -,         '   ^  •     '  i 

ciated  with  the  terminal  arms 
of  the  postnotum  (fig.  22.  PX  and  pt^).  This  sclerite  might  be 
regarded  as  the  fourth  ])arai)teruiii.  but  it  is  much  more  probably 
the  represeiitatiye  of  a  Muall  terminal  bar  of  the  postnotum  i)re.sent  in 
other  Ilymenoptera,  such  as  Pcpsis,  which  connects  this  tergal  plate 
with  the  epimeruiVK  thougli  in  this  genus  it  is  not  detached  from  the 
main  postnotal  sclerite. 

Botli  tlie  mesosternum  (i\<r.  20,  A',)  and  tlie  metasternum  [S.,)  con- 
tribute to  the  formation  of  a  large  entosternum  (/^'/^+.j),  which  forms 
a  ])r()tectinir  bridge  over  the  ('()inl)ine(l  me-^othoracic  and  metathoracic 
ganglia  (fig.  52)  and  a  fiords  attacliinent  for  the  ventral  longitudinal 
muscles  of  the  thorax   (lig.  27,  Intel). 

The  metathorax  consists  of  a  very  narrow  series  of  plates  (fig.  21, 
7'.,.  /v.,,  and  />»/.,)  c()mj)resse(l  between  tlie  mesothorax  and  the  first 
abdominal  tergum  {IT).  Its  back  plate  is  a  single,  narrow,  transverse 
xlei-ite  (figs.  21  and  2:)A,  7'.,)  widening  on  the  sides,  where  it  carries 
the  wings  by  the  1  wo  wing  processes  (fig.  23  A,  ANP  and  PXP) .    The 


THE   THORAX   AND    ITS   APPEXDACiEft. 


5,7 


ordinary  tergal  divisions  seem  to  be  entirely  o!)lit(>i-a(('(l.  Tlie  meta- 
pleurnni  consists  of  a  dorsal  platt^  iii*^.  '2\,  PI.,)  siipportina*  the  hind 
wine:  and  of  a  ventral  jjlate  (pi:.)  earryinir  the  hind  le<i:.  These  two 
fnnctions  certainly  identify  these  two  plates  as  constituting  together 
the  nietaplenruni,  hut  there  is  absolutely  no  trace  of  a  divu^ion  into  an 
episternuni  aiul  an  epimerum.  Once  more,  there foi-e,  we  have  to  go 
back  to  the  generalized  Hymenoptera  to  find  out  what  has  haj^pened. 

,5ct 


Fig.  23. — A,  thoracic  terga  of  worker  separated  from  one  another,  showing  protergum 
{Ti),  mesotergum  (7  2)  and  its  internal  postscutellum  (postnotum  PN2)  and  phragma 
(PpTza),  metatergum  (Ts)  and  propodeum  or  first  abdominal  torgum  (IT)  ;  B,  ventral 
view  of  principal  or  notal  plate  of  mesotergum. 

The  answer  is  simple.  StJ^ex  has  a  typical  nietapleurum  consisting  of 
an  episternum  and  epimerum  separated  by  a  complete  pleural  suture. 
In  the  higher  forms  this  suture  simply  disappears,  and  consequently 
the  pleurum  shows  no  traces  of  its  original  component  plates.  The 
division  into  a  wing-bearing  and  a  leg-bearing  plate  is.  therefore,  a 
purely  secondary  one. 

None  of  the  Hymenoptera  has  separate  trochantinal  sclerites  (see 
fig.  4,  Tn)j  but,  since  the  coxse  are  articulated  ventrally  to  knobs 


58 


THE   ANATOMY    OF   THE   HONEY   BEE. 


(figs.  20  and  21.  .a)  apparently  belonging  to  the  sterna,  it  might  be 
supposed  that  the  trochantins  have  fused  with  the  latter  plates. 

The  posterior  part  of  the  thoracic  mass  (fig.  21)  consists  of  the 
first  abdominal  tergum  (/T).  which  fits  into  the  deeply  concave  pos- 
terior edges  of  the  metathorax  and  forms  the  peduncle  (Pd)  that 
carries  the  rest  of  the  abdomen  (fig.  32).  It  consists  of  a  single  large, 
strongly  convex  sclerite  (figs.  21  and  23  A,  IT)  bearing  the  first 
abdominal  sj^iracles  laterally  {IS]))  and  having  its  surface  divided 
into  several  areas  by  incomplete  sutures. 

Many  entomologists  find  it  difficult  to  believe  that  this  plate,  which 
so  apparently  belongs  to  the  thorax,  is  really  derived  from  the  abdo- 
men. But  the  proof  is  forthcoming  from  a  number  of  sources.  In 
the  first  place,  the  thorax  is  complete  without  it  and  the  abdomen  is 
incomplete  without  it,  the  latter  having  otherwise  only  nine  seg- 
ments.    Again,  if  the  plate  is  reckoned  as  a  part  of  the  thorax  we 


WP. 


WP, 


A  B 

Fig.  24. — A.  upper  part  of  loft  mosoplounim  of  workor,  oxt(>rnnl  :  R.  inn«n-  view  of  same. 

should  have  the  anomaly  of  a  thorax  with  three  pairs  of  spiracles — 
there  being  the  normal  two  on  each  side  situated,  as  they  always  are, 
between  the  true  thoracic  segments.  Furthermore,  comparative  anat- 
omy shows  us  that  in  some  of  the  sawfiies  (Tenthredinida^)  the  first 
abdominal  tcrgiim.  while  se})arated  by  a  wide  membranous  space 
from  the  second,  is  not  at  all  incorporated  into  the  thorax.  In  a  horn- 
tail  such  as  S/rr,/'  (Sirici(Ue)  the  entire  first  abdominal  segment  is 
fused  to  the  posterior  edge  of  the  metathorax  and  is  only  loosely 
joined  to  the  next  abdominal  segment  by  membrane.  This  insect 
all'ords,  therefore,  a  most  complete  demonstration  of  the  transference 
of  this  segment  from  the  rest  of  the  abdomen  to  the  thorax.  Finally, 
we  have  absolute  proof  of  its  abdominal  origin  based  on  a  knowledge 
of  development,  foi"  it  has  been  shown  by  Packard  from  a  study  of  the 
bumblebee  that  the  first  abdominal  segment  of  the  larva  is  trans- 
ferred duiing  the  pu])al  metamorphosis  to  the  thorax  and  forms  the 


THE    THORAX    AND    ITS   APPENDAGES.  59 

part  uiuler  discussion.  A\\'  hence  see  that  not  only  tlie  first  abdomi- 
nal tergum  but  the  entire  segment  has  undergone  transposition, 
though  the  ventral  part  has  disappeared  in  all  the  higher  families*. 
This  transferred  part  has  been  named  both  the  median  segment  and 
the  j)TOj>odeum  by  writers  who  recognize  it  as  belonging  to  the  abdo- 
men and  not  to  the  thorax. 

The  names  current  among  systematists  for  the  back  plates  of 
Hymenoptera  afford  an  excellent  example  of  the  errors  that  ento- 
mologists may  be  led  into  through  an  ignorance  of  the  comparative 
anatomy  of  insects.  They  recognize  the  protergum  as  such  and  then, 
laiowing  that  there  are  yet  two  segments  to  be  accounted  for,  they 
call  the  mesoscutum  the  "  mesonotum,"  the  mesoscutellum  the 
"  scutellum,''  the  meta tergum  the  **  postscutellum  *'  (being  unaware 
that  the  true  postscutellum  is  deeply  concealed  within  the  thorax), 
while  the  first  abdominal  tergum  is  called  the  metathorax.  Such 
a  nomenclature  assigns  both  pairs  of  wings  to  the  mesothorax.  Too 
many  systematists  working  in  only  one  order  of  insects  do  not  care 
whether  their  names  are  applied  with  anatomical  consistency  or  not. 

2.    THE   WINGS   AND  THEIR   AKTICILATION. 

In  the  study  of  insects  the  wings  always  form  a  most  interesting 
subject  because  by  them  insects  are  endowed  with  that  most  coveted 
function — the  power  of  flight.  It  has  already  been  stated  that  the 
wings  are  not  primary  embryonic  appendages,  but  are  secondary  out- 
growths of  the  body  wall  from  the  second  and  third  thoracic  seg- 
ments. Therefore  it  is  most  probable  that  the  early  progenitors  of 
insects  were  wingless,  yet  for  millions  of  years  back  in  geological  time 
they  have  possessed  these  organs  in  a  pretty  well  developed  condition. 

Xearly  all  of  the  insect  orders  have  some  characteristic  modifica- 
tion of  the  wing-veins  and  their  branches.  Xone  of  them,  however, 
departs  nearly  so  far  from  the  normal  type  as  do  the  Hymenoptera, 
even  the  lowest  members  of  this  group  possessing  a  highly  specialized 
venation.  Before  beginning  a  study  of  the  Hymenopteran  series 
which  leads  up  to  .the  bee  the  student  should  first  turn  back  to  figure 
0  (p.  22)  and  again  familiarize  himself  with  the  generalized  condi- 
tion of  the  veins  and  the  articular  elements  of  the  wing.  By  com- 
paring, now,  with  this  diagram  the  basal  parts  of  the  wing  of  a 
sawfly  {Itycorsia  discolor^  fig.  26  A)  it  will  be  easy  to  identify  the 
parts  of  the  latter.  Vein  C  has  two  little  nodules  ((?,  C)  cut  off  from 
its  basal  end  which  lie  free  in  the  axillary  membrane.  Vein  Sc  articu- 
lates by  an  enlarged  and  contorted  base  {Sc)  with  the  first  axillary 
(lAx)^  while  vein  R  is  continuous  with  the  second  {2 Ax).  The  next 
two  veins  that  come  to  the  base  and  unite  with  each  other  are  appar- 
ently not  the  media  and  cubitus  but  the  first  and  third  anals  {lA  and 


60 


THE   ANATOMY   OF   THE   HONEY   BEE. 


3A),  since  they  are  associated  with  the  third  axiUary  (oAx) .  In  this 
species  the  subcosta  (8c)  is  entirely  normal,  but  in  the  related  horntail 
{Slrex  fiaviconiis,  fig.  26  B)  the  enlarged  basal  part  of  the  subcosta  is 
almost  separated  from  the  shaft  of  the  vein,  while  the  latter  (fig.  25 A 
Sc)  is  short  and  weak.  A  study  of  the  venation  of  this  wing  leads 
us  to  believe  that  the  vein  which  arises  from  the  radius  a  short  dis- 
tance from  its  base  is  the  cubitus  (Cu).     Therefore  the  basal  part 


Sc         ^       P 


R+M 


R±M 


ic          U 

\ 

__-^s:»-r — 

B^ 

Cu 

^ 

^^^^ 

^A~^==4^             \ 

r... 

■R+M, 

Hk           \ ^ 

c 


D 

Fig.  25. — Wings  of  Hymeuoptera  and  their  basul  articular  sclerites  (lAx-^Ax)  :  A,  Sircx 
fluvicornis,  front  wing;  B,  I'vpsis  sp.,  front  wing;  C,  honey  bee,  front  wing;  D,  honey 
bee,  hind  wing. 

of  the  media  is  either  gone  or  is  fused  with  the  radius.  Since  we  dis- 
cover its  branches  in  the  distal  field  of  the  wing,  arising  from  the 
trunk  of  the  radius,  we  conclude  that  the  latter  is  the  case.  By  this 
sort  of  reasoning  wo  may  arrive  at  the  Comstock  and  Needham  inter- 
I)retation  of  the  wing  illustrated  at  .1,  fig.  25.  From  this  it  is  evident 
that  the  branches  of  both  the  radius  and  the  media  have  been  bent 
back  toward  the  ])osteri(>r  margin  of  the  wing. 


THE   THOEAX   AND   ITS   APPENDAGES. 

C 

Sc. 


61 


Fig.  26. — Basal  elements  of  wings  of  Hymenoptera  :  A,  base  of  front  wing  of  a  sawfly 
(Itycorsia  discolor)  showing  comparatively  generalized  arrangement  of  veins  and 
axillaries  ;  B,  bases  of  anterior  veins  of  front  wing  of  a  horntail  {i^irex  flavicornis) , 
showing  detachment  of  base  of  subcostal  vein  (8c)  from  its  shaft;  C,  corresponding 
view  of  anterior  veins  in  front  wing  of  a  tarantula-killer  (Pepsis  sp.).  showing  com- 
plete absence  of  shaft  of  subcosta,  but  presence  of  basal  part  (Sc)  fused  with  base  of 
radius  (/>')  ;  D.  axillai-ies  of  anterior  wing  of  honey  bee  worker:  E,  tegula  of  worker; 
F,  base  of  anterior  wing  of  worker  showing  absence  of  shaft  of  subcosta  but  presence 
of  scale  (Sc)  derived  from  its  base  ;  ii,  axillaries  of  hind  wing  of  worker,  the  fourth  ab- 
sent in  bee  ;  H,  base  of  hind  wing  of  worker,  showing  absence  of  costal  and  subcostal  veins 
and  fusion  of  bases  of  subcosta  (So)  and  radius  (R)  into  large  humeral  mass;  I,  attach- 
ment of  front  wing  to  scutum  (Sct■2^  and  scutellum  (Scl^)  of  mesotergum  :  J.  under  view 
of  pnd  of  mososcut(-llum  (Sclj)  showing  attachment  of  both  first  U-lJ"^  and  fourth 
axillaries  (^Ax)  to  posterior  wing  process  (FNF),  an  unusual  connection  for  first  axillary. 


62  THE  ANATOMY  OF  THE  HONEY  BEE. 

Taking  this  wing  of  Sirex  as  a  foundation  let  us  proceed  a  little 
higher  and  examine  the  wing  of  a  Pompilid,  such  as  Pepsis  (figs. 
26  C  and  25  B).  We  observed  that  in  Sirex  (fig.  20  B)  the  basal 
part  of  vein  Sc  is  almost  separated  from  the  distal  shaft.  In  Pepsis 
(fig.  26  C)  it  is  entirely  a  separate  piece,  to  which  is  fused  also  the 
base  of  vein  R.  Moreover,  the  shaft  of  Sc  has  disappeared  entirely 
(fig.  25,  B).  Thus  there  is  at  the  humeral  angle  of  the  wing  a  large 
chitinous  mass  (fig.  26  C,  Sc  and  R)  representing  the  fused  bases 
of  both  the  subcosta  and  the  radius,  which  is  associated  with 
botli  the  first  axillary  {lAx)  and  the  second  axillary  {2 Ax). 

If  now  we  proceed  to  a  study  of  the  front  wing  of  the  bee  we 
find  that  its  basal  characters  (fig.  26  F)  are  more  similar  to  those  of 
S'tirx  (B),  while  its  venati.{)n  (fig,  25  C)  resembk^s  more  closely  that 
of  Pepsis  (B).  The  subcostal  scale  at  its  base  (fig.  26  F,  Sc)  is 
not  fused  with  the  base  of  the  radius,  but  the  distal  part  of  the 
subcosta  is  gone  (fig.  25  C),  as  in  Pepsis.  In  the  hind  wing  of  the 
bee  (fig.  26  H)  the  bases  of  the  subcosta  and  radius  are  fused  into 
one  large  humeral  mass  articulating  with  the  first  two  axillaries 
{lAx  and  2Ax).  The  third  axillary  {-hlx)  is  well  developed  but 
the  fourth  is  absent.  The  venation  (fig.  25  D)  is  reduced  to  a  very 
simple  condition,  but  to  one  just  the  opposite  from  primitive. 

The  details  of  the  axillaries  in  tlu^  two  wings  are  shown  by  figure 
26  D  and  G.  The  fourth  {JfAx)  is  well  developed  in  the  front  wing 
(I))  and  has  a  large  accessory  sclerite  (//)  connected  with  it,  upon 
which  is  inserted  a  long  slender  muscle  (fig.  28,  cc).  A  very  small 
accessory  sclerite  {ax)  occurs  close  to  the  muscle  plate  of  the  third 
axillary  {3 Ax).  These  are  called  "accessory''  sclerites  because 
they  are  of  irregular  occurrence  in  the  wing  bases  of  insects  generally 
and  are  develoj)ed  in  connection  with  the  muscle  attachments.  Simi- 
lar ones  occur  in  the  hind  wing  ((i,  <fx)  in  connection  with  the 
second  (2 Ax)  and  third  axillaries  {3 Ax). 

The  front  wing  is  attached  to  the  posterior  half  of  the  side  of 
the  mesonotum.  The  anterior  notal  wing  process  is  bilobed  (figs. 
22,  2.*^  A,  7'..,  .1A7*)  and  is  carried  by  the  scutum,  while  the  ])()s- 
terior  process  {PNP)  is  carried  by  the  scutellum  and  is  mostly 
hidden  beneath  the  anterior  wing  process.  The  two  wing  processes, 
in  fact,  are  so  close  togethei'  that  the  first  axillary  articidates  not 
only  with  the  first  but  also  Avith  the  second  (fig.  2()  J).  The  axillary 
coimI  dig.  26  F.  .1,/'^)  jiiMscs  from  a  lobe  of  the  scutellum  overlapjUMl 
by  the  lateral  margin  (I  and  J.  AxC).  In  the  hind  wing,  wIhmv  the 
I'oui'th  axillai-y  is  absent,  tiu*  third  articulates  directly  with  the 
l)osterioi-  notal  wing  process  of  the  metatergum  (fig.  23  A,  7\,  PXP). 

The  base  of  (he  front  wing  is  ()verlai)pe(l  by  a  lai'ge  scale  ({\ii.  26, 
10  and   I.  T(j)  caHed  the  (eguhi.      It   is  carried  by  the  axillary  mem- 


THE    THORAX   AND   ITS   APPENDAGES.  63 

brane,  to  which  it  is  atttiched  between  the  liiiiiieral  angle  of  the  wing 
base  and  the  edge  of  the  noluni.  The  teguhx'  are  })resent  in  most  in- 
sects, generally  on  the  base  of  each  wing,  but  they  usually  have  the 
form  of  small  inconsi)icuous  hairy  pads,  as  ^hown  in  the  diagram 
(fig.  (),  T(j).  In  the  liies,  moths,  butterflies,  and  llymenoptera, 
however,  the  tegular  of  the  front  wings  develop  into  large  conspicu- 
ous scales  overlapping  the  humeral  angles  of  the  bases  of  these 
wings. 

The  motion  of  the  wing  in  flight  consists  of  both  an  up-and-down 
movement  and  a  forward-and-backward  movement,  which  two  com- 
bined cause  the  tip  of  the  wing  to  describe  a  figure-eight  course  if 
the  insect  is  held  stationary.  Corresponding  with  these  four  move- 
ments are  four  sets  of  muscles.  Tn  the  dragonflies  nearly  all  of  the 
wing  muscles  are  inserted  directly  upon  the  base  of  the  wing  itself, 
but  in  other  insects,  excepting  possibly  the  mayflies,  the  principal 
muscles  are  inserted  upon  the  thoracic  walls  and  move  the  wing 
secondarily.  In  the  lower  insects,  such  as  the  grasshoppers,  crickets, 
stoneflies,  net-winged  flies,  etc.,  the  two  wing-bearing  segments  are 
about  equal  in  their  development  and  each  is  provided  with  a  full 
equipment  of  nmscles.  In  these  insects  the  wings  Avork  together  by 
coordination  of  their  muscles,  although  each  pair  constitutes  a  sepa- 
rate mechanism.  In  such  insects,  however,  as  the  true  flies  and  the 
wasps  and  bees  the  metathorax,  as  we  have  seen  in  the. case  of  the 
bee,  is  greatly  reduced,  and  what  is  left  of  it  is  solidly  attached  to 
the  mesothorax.  In  the  flies  the  hind  wings  are  reduced  to  a  pair 
of  knobbed  stalks  having  no  function  as  organs  of  flight,  while  in 
the  bees  the  hind  wings,  which  are  very  small,  are  attached  to  the 
front  wings  by  a  series  of  booklets  on  their  anterior  margins  (fig. 
25  D,  Hh)  Avhich  grasp  a  posterior  marginal  thickening  of  the 
front  wings.  Moreover,  when  we  examine  the  interior  of  the  bee's 
thorax  we  find  that  the  muscles  of  the  metathorax  are  greatly 
reduced  or  partly  obliterated  and  that  the  great  mesothoracic  mus- 
cles serve  for  the  movement  of  both  wings,  thus  assuring  a  perfect 
synchrony  in  their  action.  Hence,  it  is  clear  that  the  union  and 
consolidation  of  the  thoracic  segments  in  the  higher  insects  is  for 
the  purpose  of  unifying  the  action  of  the  wings. 

The  muscles  of  flight  in  the  bee  may  be  very  easily  studied  by  cutting 
the  thorax  of  a  drone  into  lateral  halves.  The  cavity  of  the  thorax 
is  occupied  almost  entirely  by  three  great  masses  of  muscles.  One 
of  these  is  longitudinal,  median,  and  dorsal  (fig.  27,  LMcl^)^  extend- 
ing from  the  mesoscutum  {Set.,)  and  the  small  prephragma  {Aph) 
to  the  large  mesothoracic  postphragma  (Pph.,).  A  small  set  of 
muscles  {LMcl^)  then  connects  the  posterior  surface  of  this  phragma 
with  the  lower  edge  of  the  propodeum  {IT),     On  each  side  of  the 


64 


THE   ANATOMY    OF    THE    HONEY   BEE. 


UAcl: 


anterior  end  of  this  great  longitudinal  muscle  is  a  thick  mass  of 
dorso- ventral  fibers  (VMcl)  extending  from  the  lateral  areas  of  the 
mesoscutum  (Set.,)  to  the  lateral  parts  of  the  mesosternum  (S.^).  A 
contraction  of  the  vertical  muscles  must  depress  the  tergal  parts, 
at  the  same  time  expanding  the  entire  thorax  in  a  longitudinal  direc- 
tion and  stretching  the  longitudinal  muscles.  A  contraction,  then, 
of  the  latter  muscles  {LMci)  restores  the  shape  of  the  thorax  and 
elevates  the  tergal  parts.     Remembering,  now,  that   the  wings  are 

supported  from  be- 
low upon  the 
pleural  wing  proc- 
esses and  that  each 
is  hinged  to  the 
back  by  the  notal 
wing  processes,  it 
is  clear  that  a  de- 
pression of  the 
dorsum  of  the 
thorax  must  ele- 
vate the  wings  and 
that  an  elevation 
of  the  dorsum  de- 
presses them — the 
pleural  wing  proc- 
esses acting  as  the 
fulcra.  Hence,  the 
chief  up-and-down 
movements  of  the 
wings  are  pro- 
duced by  these 
great  thoracic  mus- 
cles acting  upon 
the  shape  of  the 
thorax  as  a  whole 
and  not  directly 
upon  the  wings 
themselves.  The  vertical  muscles  are  the  elevatovfi  and  the  longi- 
tudinal the  dejncsHors. 

I>iit  besides  being  moved  up  and  down  the  wings  can  also,  as  before 
stated,  be  extended  and  flexed,  i.  e.,  turned  forward  and  backward  in 
a  hoiizontal  plane  upon  the  pleural  wing  process.  The  nniscles 
wliich  accomplisli  these  movements  lie  against  the  inner  face  of  the 
pleurum  (fig.  28),  and  each  wing  is  provided  with  a  separate  set. 
Tlie  extensoi-  muscle  {PMcl)  is  (he  most  anterior  and  is  inserted  hy 
a  long  neck  upon  the  prej)arapterum    {2P).     The  latter  is  closely 


Fig.  27. — Median  section  through  thorax  of  drone,  showing 
longitudinal  muscles  {LMc'12)  of  mesothorax  going  from 
mesotergal  scutum  (Scto)  and  small  anterior  phragma 
iAph)  to  posterior  phragma  {Pph-z)  of  internal  postscutel- 
lum  (postnotum)  of  same  segment,  also  showing  vertical 
mesothoracic  muscles  (VMcl),  and  ventral  longitudinal  mus- 
cles {hncl),  and  longitudinal  muscles  of  metathorax 
(LMch)  going  from  postphragma  of  mesothorax  (Pph,)  to 
posterior  edge  of  propodeum  or  first  abdominal  tergum  (IT). 
By  alternate  contraction  of  dorsal  longitudinal  muscles  and 
vertical  muscles,  roof  of  thorax  is  elevated  and  depressed, 
causing  wings  to  boat  downward  and  upward  respectively, 
being  supported  on  fulcra  formed  by  pleural  wing  processes 
(fig.  28,  WP2)  of  side  walls  of  thorax. 


THE    THORAX   AND    ITS    APPENDAGES. 


G5 


WR  2Ax  3Ax 


connected  with  the  anterior  part  of  tlie  base  of  tlie  win^  so  that  ii 
contraction  of  the  muscle  turns  the  wing  forward  and  at  the  same 
time  depresses  its  anterior  margin.  For  this  reason  the  parapterum 
and  the  extensor  muscle  liave  been  called  tlie  proxdfor  appdratm^^  and 
the  muscle  is  known  also  as  the  pronator  musrle.  Tn  some  insects 
which  fold  the  wings  back  against  the  body  this  muscle  is  a  great 
deal  larger  than  iii  the  bee.  The  fexor  muscle  (RMcl)  consists  of 
three  parts  situated  upon  the  anterior  half  of  the  pleurum  and  in- 
serted upon  the  third  axillary  (SAx)  by  long  tendonlike  necks. 
These  muscles  are  antagonistic 
to  the  extensor  and  by  their 
contraction  pull  the  wing 
back  toward  the  body. 

The  mechanism  Avhich  pro- 
duces the  Aving  motion  thus 
seems  to  be  a  very  simple  one 
and  may  be  summarized  as 
follows:  Each  wing  rests  and 
turns  upon  the  wing  process 
of  the  pleurum  (figs.  24  and 
28,  WP)  by  means  of  the 
pivotal  sclerite  or  second  axil- 
lary in  its  base  (figs.  26  F^^nd 
28,  2 Ax).  It  is  hinged  tp  the 
back  by  the  first  and  fourth 
axillaries  (fig.  26  F,  lAx  and 
4 Ax)  which  articulate  with 
the  anterior  and  posterior 
notal  wing  proces^^  (fig.  23 
A,  T,,  ANP  and  PXP),  re- 
spectively. The  large  vertical 
muscles  (fig.  27,  VJ/cl)  of 
the  thorax  depress  the  ter- 
gum.  which  pulls  down  with 
it  the  base  of  the  wing  and 
hence  elevates  the  distal  part — 
the  fulcrum  being  the  pleural  wing  process.  The  dorsal  longitudinal 
muscle  {LMcl)  restores  the  shape  of  the  thorax,  elevates  the  tergum, 
and  consequently  depresses  the  wing.  Extension  and  flexion  of  the 
wing  are  produced  by  special  muscles  (fig.  28,  PMd  and  RMcl)  acting 
upon  its  base  before  and  behind  the  pleural  wing  process,  respectively. 

Besides  these  muscles  there  are  several  others  (fig.  28)  associated 

with  the  wing  whose  functions  are  less  evident.     Most  conspicuous 

of  these  is  a  muscle  occupying  the  posterior  half  of  the  mesopleurum 

{aa)  and  inserted  upon  the  outer  end  of  the  scutellum.     This  may 

22181— No.  18—10 5 


Fig.  28. — Internal  view  of  right  pleurum  of 
mesothorax  of  drone,  sliowing  muscles  in- 
serted upon  parapteral  plates  {2P  and  3P) 
and  upon  third  axillary  {3Ax).  The  wing 
rests  upon  wing  process  of  pleurum  (TFP2) 
by  second  axillary  (24a?)  ;  it  is  turned  for- 
ward and  downward  by  the  pronator  muscle 
{PMcl),  inserted  upon  anterior  parapterum 
(2P)  which  is  attached  to  costal  head  of 
wing,  and  is  turned  back  toward  body  by 
flexor  muscle  {RMcl)  inserted  upon  third 
axillary    {3 Ax). 


66  THE  ANATOMY  OF  THE  HONEY  BEE. 

be  simply  accessory  to  the  large  vertical  sterno-sciital  muscle  (fig.  27, 
VMcl).  Another  is  a  long  slender  muscle  {hh)  attached  to  the  upper 
end  of  the  mesocoxa  and  inserted  upon  the  postparapterum  {3P).  . 
This  is  sometimes  termed  the  c ox o- axillary  muscle.  A  third  {cc)  is 
inserted  upon  the  tip  of  the  accessory  sclerite  {y)  of  the  fourth 
axillary  and  is  attached  to  the  lateral  arm  of  the  large  entosternum 
of  the  mesothorax  and  metathorax. 

3.    THE    LEGS. 

The  legs  of  the  honey  bee  are  highly  modified  for  several  special 
purposes  besides  that  of  walking,  but  they  are  so  well  known  and 
have  been  so  often  described  that  it  will  not  be  necessary  to  devote 
much  space  to  them  here. 

The  front  legs  (fig.  29  A)  have  a  structure  formed  by  the  adjoining 
ends  of  the  til)ia  and  the  first  tarsal  joint,  which  is  called,  on  account 
of  its  use,  the  antenna  cleaner.  It  consists  (fig.  29  C)  of  a  semi- 
circuhir  notch  {dd)  in  the  base  of  the  first  tarsal  joint  provided 
with  a  comblike  row  of  bristles.  A  si)ecially  modified.  Hat,  movable 
spur  (<?<^0?  shown  in  ventral  view  at  B,  is  so  situated  on  the  end  of 
the  tibia  {Th)  that  it  closes  over  the  notch  when  the  tarsus  is  bent 
toward  the  tibia.  By  grasping  an  antenna  between  the  notch  and 
the  spur  and  drawing  it  through  the  inclosure  the  bee  is  able  to  re- 
move from  this  sensitive  appendage  any  pollen  or  particles  of  dirt 
that  may  be  adhering  to  it. 

The  middle  legs  (fig.  29  D)  present  no  special  modifications  of  any 
imj)ortance.  It  will  be  observed,  hoAvever,  that  they,  as  well  as  the 
other  legs  (A  and  F),  have  the  first  joint  of  the  tarsus  {ITar)  very 
greatly  enlarged. 

The  hind  legs  of  all  three  forms,  the  worker  (F),  the  queen  (E),  and 
the  drone  (II),  have  both  the  tibia  and  the  large  basal  segment  of 
the  tarsus  very  much  flattened.  In  the  queen  and  drone  there  seems 
to  be  no  special  use  made  of  these  parts,  but  in  the  worker  each  of 
these  two  segments  is  modified  into  a  very  important  organ.  The 
outer  surface  of  the  tibia  (F,  Th)  is  fringed  on  each  edge  by  a  row  of 
long  curved  hairs.  These  constitute  a  sort  of  basket  {Ch\  in  which 
the  pollen  collected  from  flowers  is  carried  to  the  hive.  The  struc- 
tures are  kuown  as  the  pollen  Ixixl'cts,  or  corhJculd.  The  iuner  sur- 
face of  the  large,  flat,  basal  segment  of  the  tarsus  {ITar)  is  pro- 
vided with  several  rows  of  short  stiff  s])ines  (O)  forming  a  brush  by 
means  of  which  the  bee  gathers  the  polleu  froui  its  body,  since  it 
often  becomes  covered  with  this  (hist  from  the  (lowers  it  visits  for 
the  purpose  of  getting  nectar.  AMien  a  suiricient  amount  is  accumu- 
lated on  the  bi'ushes  it  is  s('ra])e(l  otl'  fi'om  each  over  the  edge  of  the 
tibia  of  the  ()pi)()site  hind  leg  nnd  is  thus  stored  in  the  ])()llen  baskets. 
Hence  the  worker  often  flies  back  to  the  hive  with  a  jxreat  mass  of 


THE   TilOiUX  AiS'D   US  APPENDAGES. 


67 


Fig.  29. — A,  left  front  leg  of  worker,  anterior  view,  showing  position  of  notch  {dil)  of 
antenna  cleaner  on  base  of  first  tarsal  joint  (iTar)  and  of  closing  spine  (ec)  on  end 
of  tibia  (Th)  ;  B,  spine  of  antenna  cleaner  (cc)  in  flat  view;  C,  details  of  antenna 
cleaner  ;  D,  left  middle  leg  of  worker,  anterior  view  ;  E,  left  hind  leg  of  queen,  anterior 
or  outer  view  ;  F,  left  hind  leg  of  worker,  anterior  or  outer  view,  showing  the  pollen 
basket  (Cb)  on  outer  surface  of  tibia  (Th)  ;  G,  inner  view  of  first  tarsal  joint  of  hind 
leg  of  worker  showing  rows  of  pollen-gathering  hairs  and  the  so-called  "  wax  shears  "' 
iff)  ;   II,  left  hind   leg  of  drone,  anterior  or  outer  view. 


68 


THE   ANATOMY    OF    THE    HONEY   BEE. 


pollen  adhering  to  each  of  its  hind  legs.     The  pollen  baskets  are 
also  made  use  of  for  canying  propolis. 

Between  the  ends  of  the  hind  tibia  {Th)  and  the  first  tarsal  joint 
{ITar)  is  a  sort  of  pincerlike  cleft  (F  and  G.  if)  guarded  by  a  row 
of  short  spines  on  the  tibial  edge.  This  is  popularly  known  as  the 
"  wax  shears  "  and  it  is  supposed  to  be  used  for  picking  the  plates 
of  wax  out  of  the  wax  pockets  of  the  abdominal  segments.  The 
writer,  however,  has  watched  bees  take  the  wax  from  their  abdomen 
and  in  these  observations  they  always  poked  the  wax  plates  loose 


Fig.  .30. — \,  dorsal  view  of  ond  of  last  tarsal  .ioint  of  first  foot  {Tar),  the  claws  (Cla), 
and  ompodium  (Ernp)  of  worker;  B.  ventral  view  of  same;  C,  lateral  view  of  same, 
showing  enipodiiiiii  in  ordinary  position  when  not   in  use. 

with  the  ordinary  hairs  or  spines  of  the  tibia^  or  tarsi  and  then  by 
means  of  tlie  feet  passed  them  forward  beneath  the  body  to  the 
mandibles. 

The  last  tarsal  joint  of  each  leg  bears  a  pair  of  claws  (E,  Cla^  and 
a  single  iii('(li;iii  <  iii pod'nnu  {litnp).  Each  one  of  the  claws  is  bi- 
IoIxmI.  (•<)ii>i>tiiig  of  a  long  tapering  onter  j)()int  and  a  smaller  inner 
one  ( ligs.  :)()  and  '-W).  'V\w  claws  of  the  workei-  (tig.  lil  A)  and  the 
(|neen  (  I^  are  only  slightly  dillei'ent  in  details  of  outline,  although 
the  claws  of  the  (jiieen   are  much  greater  in  size  than  those  of  the 


THE    ABDOMEN,    WAX    (iEAXDS,    AND    S'l'INCJ. 


69 


iiiial 
1    its 


worker,  but  the   drone's  claws    {C)    are   lar^-e   and    wry   slril 
different  in  shape  from  those  of  either  the  worker  ov  the  <iiieeii. 

The  enipodiuni  (fig.  J30  A,  B,  and  C,  Kinjf)  consists  of  a  tei 
iobe  bent  upward  between  the  claws  (C)  and  deeply  cleft 
dorsal  surface  (A),  and  of  a  thick  basal  stalk 
whose  walls  contain  a  number  of  chitinous 
plates.  One  of  these  plates  is  dorsal  (A  and 
C,  hh)  and  bears  five  very  long,  thick,  curved 
hairs  projecting  posteriorly  over  the  terminal 
lobe,  while  a  ventral  plate  (B  and  C,  ii)  is 
provided  with  numerous  short  thick  spines. 
A  third  plate  (A,  B,  and  C,  gg)  almost 
encircles  the  front  of  the  terminal  lobe,  its 
upper  ends  reaching  to  the  lips  of  the  cleft. 

When  the  bee  walks  on  any  ordinary  sur- 
face it  uses  only  its  claws  for  maintaining  a 
foothold,  but  when  it  finds  itself  on  a  smooth, 
slippery  surface  like  glass  the  claws  are  of  no 
avail  and  the  empodia  are  provided  for  such 
emergencies  as  this.  The  terminal  lobe  is 
pressed  down  against  the  smooth  surface  and 
its  lateral  halves  are  flattened  out  and  adhere 
by  a  sticky  liquid  excreted  upon  them  by 
glands  said  to  be  situated  in  front  of  them, 
the  muscle  that  flattens  the  empodial  lobes  the  latter  spring  back 
into  their  original  position  by  the  elasticity  of  the  chitinous  band 
{gg)  in  their  walls. 


Fig.  31. — A,  outer  view  of 
hind  claw  of  worker ;  B, 
same  of  queen ;  C,  same 
of  drone. 

On  the  relaxation  of 


V.    THE  ABDOMEN,  WAX  GLANDS,  AND  STING. 

The  abJomen  of  the  worker  and  queen  appears  to  consist  of  six  seg- 
ments (figs.  1,  32,  33,  //-TV/),  but  it  must  be  remembered  that,  as 
has  already  been  explained,  the  thoracic  division  of  the  body  in  the 
Hymenoptera  includes  one  segment,  the  propodeum  or  median  seg- 
ment, which  really  belongs  to  the  abdomen  and  is  its  true  first  seg- 
ment according  to  the  arrangement  in  all  other  insects.  Hence, 
counting  the  propodeum  (figs.  21  and  32,  IT)  as  the  first,  we  find 
seven  exposed  abdominal  segments  in  the  worker  and  queen  and 
nine  in  the  drone.  Each  one  except  the  first  consists  of  a  tergum 
{T)  and  a  sternum  {S).  the  former  reaching  far  down  on  the  side 
of  the  segment,  where  it  carries  the  spiracle  {Sp)  and  overlaps  the 
edge  of  the  sternum.  The  two  plates  of  the  last  or  seventh  segment 
in  the  worker  and  queen  are  separated  by  a  cleft  on  each  side,  and 
if  they  are  spread  apart  it  is  seen  that  the  tip   of  the  abdomen 


0 


THE   ANATOMY   OF   THE   HONEY  BEE. 


incloses  a  cavity  which  lodges  the  sting  and  its  accessory  parts.  The 
end  of  the  abdomen  of  the  male  (fig.  56  D)  is  quite  different  from 
that  of  the  female,  while  in  it  parts  at  least  of  nine  segments  are 

in 

S,vaii™«miiiiiiiiiii.iiiiiiiiiiiir//,(i;iiiiii//^^^ 
lillil'lllllli'™ 


Sp  S'tn 

Fig.   32. — Lateral  view  of  abdomen   of  worker,   showing   the  propodeiiiu    {IT)    as  a   part 
of  the  abdomen,  of  which   it  is  the  true  first  segment. 

visible,  the  last  is  very  much  modified  and  is  exposed  onl}-  on  the 
sides  and  below. 

An  internal  view  of  the  ventral  plates  and  the  lateral  parts  of  the 


Fio.  .'{.".. — N'enlral  view  of  abdomen  ol" 
worker,  showing  tip  of  sting  (/Sfn)  and 
pali)uslike  appendages  (i^tnl'lii)  pro 
jectlng  from  sting  chamber  williin 
S.'V«"llMl    scmiKMil     (  1  //). 


2Clsp' 

Fig.  34. — Dorsal  view  of  ab- 
dominal sterna  of  drone, 
showing  clasping  appendages 
(K'l.sit    and    2CIfip)    of    ninth 

SCgllHMlC 


ter<rii  ill  (lie  workci-  is  shown  by  figuro  L^O,  Avliih^  a  corresponding 
\  iew  ol"  the  iiiah'  sicriia  is  ^liowii  by  li^iire  ;)1.  It  will  be  seen  that 
each  slei-iiiiiii  is  very  widely  underlapped  (viewed  from  above)  by  the 


THE   ABDOMEN,    WAX    CILANDS,    AND   STINCi.  71. 

one  next  in  front  of  it  iind  that  i\w  iiitersconiental  membrane  (J//>) 
is  reflected  from  the  middle  of  the  dorsal  surface  of  each  to  th(i 
anterior  edge  of  the  following  sternum.  By  removing  an  iudivichial 
plate  (fig.  35  A)  this  is  more  easily  shown.  It  is  also  (clearly  seen 
that  the  transverse  line  of  attachment  of  the  membrane  (Mh)  divides 
the  sternum  into  a  posterior  part  (AV),  which  is  merely  a  prolonged 
reduplication  underlapping  the  following  sternum,  and  into  an  an- 
terior part  underlapped  by  the  preceding  sternum,  llie  posterior 
half  is,  hence,  purely  external  while  the  anterior  half  forms  the  true 
ventral  wall  of  the  segment,  its  dorsal  face  being  internal  and  its 
ventral  face  external.  The  anterior  part  is  also  very  smooth  and 
shiny  and  somewhat  bilobed  and  for  this  reason  it  is  sometimes  called 
the  "  mirrors."  Its  edge  is  bounded  by  a  thickened  ridge  giving  off  a 
short  apodeme  (Ap)  on  each  side.  The  mirrors  of  the  last  four 
sterna  are  also,  and  more  appropriately,  called  the  wax  plates  because 
the  wax  is  formed  by  a  layer  of  cells  lying  over  them.  It  accumu- 
lates on  the  ventral  side  in  the  pocket  between  the  wax  plates  and  the 
posterior  underlapping  prolongation  of  the  preceding  sternum.  Wax 
is  formed  only  on  the  last  four  visible  segments,  i.  e.,  on  segments 
IV-VII,  inclusive. 

In  studying  any  part  of  the  body  Avail  of  an  insect  it  must  always 
be  borne  in  mind  that  the  chitin  is  originally  simph^  an  external  cutic- 
ular  layer  of  a  true  cellular  skin  or  epidermis  (erroneously  called 
'' h3^podermis ''  in  insects),  but  that  in  the  adult  stage  the  latter 
almost  ever^^where  disappears  as  a  distinct  epithelium.  Thus  the 
chitin  comes  to  be  itself  practically  the  entire  body  wall,  the  cell  layer 
being  reduced  to  a  ver}-  inconspicuous  membrane.  However,  in  cer- 
tain places  the  epithelium  may  be  developed  for  special  purposes. 
This  is  the  case  with  that  over  the  wax  plates  which  forms  a  thick 
layer  of  cells  that  secrete  the  wax  and  constitute  the  so-called  wax 
glands.  The  wax  is  first  secreted  in  a  liquid  condition  and  is  ex- 
truded through  minute  pores  in  the  wax  plates  of  the  sterna,  harden- 
ing on  their  under  surfaces  into  the  little  plates  of  solid  wax  with 
which  every  bee  keeper  is  acquainted. 

The  secretion  of  the  wax  has  been  studied  by  Dreyling  (1903),  who 
made  histological  sections  through  the  glands  at  different  times  in 
the  life  of  the  bee.  He  found  that  in  young,  freshly  emerged  workers 
the  epidermis  of  the  wax  plates  consists  of  a  simple  layer  of  ordinary 
epithelial  cells.  As  the  activities  of  the  bee  increase,  however,  these 
cells  elongate  while  clear  spaces  appear  betAveen  them  and,  when  the 
highest  development  is  reached,  the  epithelium  consists  of  a  thick 
laj^er  of  very  long  cells  Avith  liquid  wax  stored  in  the  spaces  betAveen 
them.  In  old  age  most  of  the  cells  become  small  again  and  in  those 
bees  that  live  over  the  winter  the  epithelium  degenerates  to  a  simple 
sheet  of  nucleated  plasma  showing  no  cell  boundaries.  It  is  thus 
evident  that  the  secretion  of  Avax  is  best  performed  during  the  prime 


72 


THE   AXATOMY   OF    THE    HOXEY   BEE. 


of  life,  w'hich  in  bees  is  at  about  17  days  of  age  or  before,  and  that 
old  bees  can  only  gather  honey  and  pollen.  Bees  do  not  normally 
secrete  wax  while  performing  the  other  more  ordinary  duties  of  their 
life.  AMien  comb  is  needed  a  large  number  of  young  bees  or  bees 
that  have  not  passed  their  prime  hang  together  in  vertical  sheets 
or  festoons  within  the  hive  and  are  fed  an  abundance  of  honey.  After 
about  twenty-four  hours  they  begin  to  construct  comb.  During  this 
time  the  wax  is  excreted  through  the  wax  plates  and  accumulates  in 

the  external  wax  pockets  below. 
It  is  poked  out  of  these  pockets  by 
means  of  the  spines  on  the  feet 
and  is  passed  forward  beneath  the 
body  to  the  mandibles.  By  means 
of  these  organs  it  is  manipulated 
into  little  pellets  and  modeled 
into  the  comb.  Drevling:  describes 
the  pores  of  the  wax  plates  as  ex- 
cessiveh"  fine,  vertical,  parallel 
canals  only  visible  in  very  thin 
sections  and  under  the  highest 
power  of  the  microscope. 

Corresponding  abdominal  sterna 
present  quite  different  shapes  in 
the  three  forms  of  the  bee  (fig.  35 
A,  B.  and  C).  In  the  queen  (B) 
the  sterna  are  much  longer  than  in 
the  worker  (A),  while  in  the 
drone  (C)  they  are  shorter  and 
have  verv  long  lateral  apodemes 
(Ap). 

The  last  three  abdominal  seg- 
ments— the  eighth,  ninth,  and 
tenth — are  very  different  in  the 
two  sexes  on  account  of  their 
modification  in  each  to  accom- 
modate the  external  organs  of  re- 
production and  v*r<r  laying.  In  the  female  these  segments  are  entirely 
concealed  within  the  seventh,  but,  in  the  male,  parts  of  both  the 
ii<i:hth  and  ninth  sefyments  are  visible  externallv. 

The  seventh  segment  of  the  drone  (counting  the  propodeum  as 
tlie  first)  is  the  last  normal  segment,  i.  e.,  the  last  one  having  a  com- 
plete tergum  and  sternum  resembling  those  of  the  anterior  part  of 
the  abdomen  (fig.  50  D,  VII 7'  and  VIIS).  Behind  the  seventh  ter- 
gum and  ])artly  concealed  within  it  is  the  eighth  tergum  (VII IT) 
carrying  the  last  abdominal  spiracles  (^p).    The  eighth  sternum  is 


Fig.  35. — Dorsal  surface  of  sixth  abdominal 
sternum  :  A,  worker  ;  B,  queen  ;  C.  dron«> ; 
showing  division  of  plate  by  line  of  at- 
tachment of  intersegmental  membrane 
(J/bi  into  anterior  part  with  polished 
internal  surface,  in  worker  Ix-arinj;  wax 
glands,  and  into  large  posterior  external 
part  {ltd)  underlapping  anterior  half  of 
succeeding  sternum. 


THE    ABDOMEX,    WAX    fiLAXDS,    AND    STTNCl.  73 

almost  entirely  concealed  within  the  seventh.  It  is  very  narrow 
below,  but  is  exj^anded  at  the  upper  parts  of  its  sides  (TV/AS'),  where 
it  is  partly  visible  below  the  eighth  tergum  and  behind  the  seventh 
sternum.  The  dorsal  part  of  the  ninth  segment  is  membranous  except 
for  a  small  apodeme-bearing  plate  on  each  side  hidden  within  the 
eighth  tergum.  The  ninth  sternum,  on  the  other  hand,  is  a  well- 
developed  semicircular  band  (IXjS)  forming  the  ventral  and  ventro- 
lateral parts  of  the  ninth  segment.  It  bears  on  each  side  two  con- 
spicuous lobes — one  a  small,  darkly  chitinized,  dorsal  plate  (IClsp) 
carrying  a  large  bunch  of  long  hairs,  the  other  a  large,  thin,  ventral 
plate  {2Clsp).  Between  these  four  appendicular  lobes  is  ordinarily  a 
deep  cavity,  Avhich  is  the  invaginated  penis  (fig.  56  E),  but  in 
figure  D  this  organ  is  shown  partly  evaginated  {Pen).  While  the 
penis  is  really  an  external  organ,  the  details  of  its  structure  will  be 
described  later  in  connection  with  the  internal  organs  of  reproduction. 
The  tenth  segment  is  entirely  lacking  in  segmental  form.  The  anal 
oi^ening  is  situated  in  a  transverse  membrane  beneath  the  eighth  ter- 
gum {VI I  IT),  and  below  it  is  a  thin  chitinous  plate,  which  may 
belong  to  the  tenth  segment. 

In  many  insects  the  modification  of  the  terminal  segments  of  the 
males  in  connection  with  the  function  of  copulation  is  much  greater 
than  in  the  bee.  The  ninth  segment  often  forms  a  conspicuous 
enlargement  called  the  liypopygium.^  which  is  usually  provided  with 
variously  developed  clasping  organs  in  the  form  of  appendicular, 
plates  and  hooks. 

The  development  of  the  external  genital  parts  of  the  drone  has  been 
described  by  both  Michaelis  (1900)  and  Zander  (1900).  A  small 
depression  first  appears  on  the  under  surface  of  the  ninth  segment  of 
the  larva  shortly  after  hatching.  Soon  two  little  processes  grow 
backward  from  the  anterior  wall  of  this  pouch  and  divide  each  into 
two.  The  part  of  the  larval  sternum  in  front  of  the  pouch  becomes 
the  ninth  sternum  of  the  adult,  while  the  two  processes  on  each  side 
form  the  upper  and  lower  appendicular  lobes  (the  valva  externa  and 
the  valva  interna  of  Zander) .  The  penis  at  first  consists  of  two  little 
processes  which  arise  between  the  valvse  internee,  but  is  eventually 
formed  mostly  from  a  deep  invagination  that  grows  forward  between 
them.  These  four  processes  arising  on  the  ventral  side  of  the  ninth 
segment  of  the  male  larva  are  certainly  very  suggestive  of  the  similar 
ones  that  are  formed  in  the  same  way  on  the  same  segment  of  the 
female  and  which  develop  into  the  second  and  third  gonapophyses 
of  the  sting.  If  they  are  the  same  morphologically  we  must  homol- 
ogize  the  two  clasping  lobes  of  the  ninth  sternum  in  the  male  with 
the  two  gonapophyses  of  this  segment  in  the  female.  Zander  (1900) 
argues  against  such  a  conclusion  on  the  ground  that  the  genital  pouch 
is  situated  near  the  anterior  edge  of  the  segment  in  the  female  and 


74  THE   ANATOMY   OF    THE    HONEY   BEE. 

posteriorly  in  the  male,  while  the  parts  in  the  two  sexes  develop 
later  in  an  absoluteh'  different  manner.  These  arguments,  how- 
ever, do  not  seem  very  forcible — in  the  earliest  stages  the  processes 
certainly  look  alike  in  the  tAvo  sexes. 

The  sting  of  the  bee  is  situated  in  the  sting  cavit}^  at  the  end  of  the 
abdomen,  from  which  it  can  be  quickly  protruded  when  occasion  de- 
mands. This  sting  chamber  contains  also  the  reduced  and  modified 
sclerites  of  the  eighth,  ninth,  and  tenth  abdominal  segments.  In 
fact,  the  sting  chamber  is  formed  by  an  infolding  of  these  three  seg- 
ments into  the  seventh.  It  is  consequently  not  a  part  of  the  true  in- 
terior of  the  body  or  body  cavity  which  contains  the  viscera,  but  is 
simply  a  sunken  and  inclosed  part  of  the  exterior,  in  the  same  sense 
that  the  oven  of  a  stove  is  not  a  part  of  the  real  inside  of  the  stove. 
Consequently  the  parts  of  the  sting,  though  normally  hidden  from 
view,  are  really  external  structures. 

A  very  gentle  pull  on  the  tip  of  the  sting  is  sufficient  to  remove  it 
from  its  chamber,  but  a  sting  thus  extracted  brings  along  with  it  the 
ninth  and  tenth  segments,  most  of  the  eighth  segment,  the  poison 
glands,  and  the  terminal  part  of  the  alimentary  canal.  This  is  due 
to  the  fact  that  the  inclosed  segments  are  attached  to  the  surround- 
ing parts  by  very  delicate  membranes.  For  the  same  reason  they  so 
easily  tear  from  the  living  bee  as  the  latter  hurriedly  leaves  its  victim 
after  stinging.  The  worker  thus  inflicts  a  temporary  Avound  and 
pain  at  the  cost  of  its  own  life.  Undoubtedly,  however,  nature  re- 
gards the  damage  to  the  enemy  as  of  more  importance  to  the  bee 
comnumit}^  as  a  whole  than  the  loss  of  one  or  a  dozen  of  its  members. 
The  entire  stinging  apparatus  with  a  bag  of  poison  attached  is  thus 
left  sticking  in  the  wound  wliile  tlie  muscles,  which  keep  on  working 
automatically,  continue  to  drive  the  sting  in  deeper  and  deeper  and 
at  the  same  time  pump  in  more  ]K)ison.  Such  a  j^rovision  certaiidy 
])r()duces  much  more  effective  results  than  would  a  bee  giving  a  thrust 
here  and  anotlier  there  witli  its  sting  and  then  rajMdly  Hying  away 
to  escape  from  danger. 

The  sting  itself,  when  extracted  from  its  chamber,  is  seen  to  cou- 
sist  of  a  straight  tai)ering  shaft  with  its  tip  directed  posteriorly  and 
its  base  swollen  into  a  bulblike  enlargement.  In  superficial  api^ear- 
ance  the  shaft  appears  to  be  solid,  although  we  shall  presently  show 
that  it  is  not,  but  the  bulb  is  clearly  hollow  and  is  open  below  by 
a  distinct  median  cleft.  Several  plates  of  definite  shape  and  arrange- 
ment always  remain  attached  to  the  sting  and  overla])  its  base.  The 
entire  a])i)aratus,  including  the  base  of  the  large  poison  sac,  is  shown 
somewhat  diagrammatically  in  side  view  by  figure  l\C).  The  bulb  of 
the  sting  (A7///)  is  connected  with  the  lateral  ])lates  by  two  arms 
which  curve  outwai^l  und  npwaid  from  its  base.  (Only  the  left  side 
is  shown  in  the  figure.)     lie! ween  these  arms  the  two  poison  glands 


THE    ABDOMEN,    WAX    (JLANDS,    AND    STINO. 


75 


{PsnSc  and  BGl)  open  into  the  anterior  end  of  tlie  bulb.  From  tin; 
posterior  ends  of  the  plates  two  whitish  fin<rerlike  processes  (StnPlp) 
project  backward.  When  the  stin*^:  is  retracted  these  lie  at  the  sides 
of  the  shaft  (figs.  83  and  87),  but  in  fi<jfure  8G  the  stin<^  is  sliown  in  a 
partly  protracted  position.  These  appendages,  often  called  the  sting 
palpi,  undoubtedly  contain  sense  organs  of  some  sort  by  means  of 
which  the  bee  can  tell  when  her  abdomen  is  in  contact  with  the  object 
upon  which  she  desires  to  use  her  sting. 

A  close  examination  of  the  sting  shows  that  it  is  a  much  more  com- 
plicated structure  than  it  at  hrst  sight  appears  to  be.  The  shaft,  for 
example,  is  not  a  simple,  solid,  tapering,  spearlike  rod,  but  is  a  hollow 
organ  made  of  three  pieces  which  surround  a  central  canal.  One  of 
these  pieces  is  dorsal  (fig.  86,  ShS)  and  is  the  true  prolongation  of 
the  bulb  (ShB),  while  the  other  two  (Let)  are  ventral  and  slide 
lengthwise  on  tracklike  ridges  of  the  dorsal  piece.  Moreover,  each 
basal  arm  of  the 
sting  is  double,  con- 
sisting of  a  dorsal 
or  posterior  piece 
(ShA)^  which  is  like- 
wise a  prolongation 
of  the  bulb,  and  a 
ventral  or  anterior 
piece  (Zc^^),  which  is 
continuous  with  the 
ventral  rod  of  the 
shaft  on  the  same 
side.  Hence  the  sting 
may  be  analyzed  into 
three  elements,  which 

are  characterized  as  follows:  The  dorsal  piece,  known  as  the  sheath, 
consists  of  a  prominent  basal  swelling  or  hulh  (ShB)  containing  a 
large  cavity,  of  a  terminal  tapering  shaft  (ShS) ,  and  of  two  curved 
hasal  arms  (ShA).  The  ventral  part  consists  of  two  long  slender 
rods,  called  the  lancets  or  darts  (Let),  which  slide  freely  upon  two 
tracks  on  the  ventral  edges  of  the  sheath  and  diverge  upon  continua- 
tions of  these  tracks  along  the  basal  arms  of  the  latter  (ShA).  The 
bulb  is  hollow,  containing  a  large  cavity  formed  by  invagination 
from  below,  where  it  is  open  to  the  exterior  by  a  lengthwise  cleft. 
This  cavity  continues  also  through  the  entire  length  of  the  shaft  of 
the  sting  as  a  channel  inclosed  between  the  dorsal  sheath  and  the 
latero-ventral  lancets.  This  channel,  as  will  be  explained  later,  is 
the  poison  canal  of  the  sting. 

Each  arm  of  the  sheath   (ShA)   is  supported  at  its  end  farthest 
from  the  bulb  by  an  oblong  plate  (fig.  86,  Oh),  which  normally  over- 


FiG.  36. — Semidiagrammatic  view  of  loft  side  of  sting  of 
worker,  accessory  plates  {Tri,  Oh,  Qd),  sting  palpus 
(stnPli)),  alkaline  poison  gland  (BGI),  and  base  of  large 
poison  sac  (PshSc)  of  acid  gland. 


76 


THE   ANATOMY   OF    THE    HOXEY    BEE. 


\ 


laps  the  side  of  the  bulb,  and  Avhich  carries  distally  the  j)alpi  of  the 
sting  (StnPJp).  Each  lancet  is  attached  at  its  base  to  a  triangular 
flate  {Tri)  which  lies  latero-dorsad  to  the  base  of  the  oblong  plate  . 
and  articulates  with  a  knob  on  the  dorsal  edge  of  the  latter  by  its 
ventral  posterior  angle.  By  its  dorsal  posterior  angle  the  triangular 
plate  is  articulated  to  a  much  larger  quadrate  plate  (Qd)  which 
overlaps  the  distal  half  of  the  oblong  plate.  A  thick  membranous 
lobe  {IXS).  concave  below,  where  it  is  thickly  set  with  long  hairs, 
overlaps  the  bulb  of  the  sting  and  is  attached  on  each  side  to  the 
edges  of  the  oblong  plates.     All  of  these  parts  are  shown  flattened  out 

in  ventral  view  by 
figure  37. 

The  presence  of 
the  two  basal  arms 
of  the  sheath  might 
suggest  that  this 
part  is  to  be  re- 
garded as  made  up 
of  fused  lateral 
halves.  In  this  case 
we  should  have  six 
appendicular  ele- 
ments, viz,  the  two 
lancets,  the  two 
halves  of  the  sheath, 
and  the  two  pal- 
puslike organs.  If 
now  we  turn  back  to 
figure  8,  showing 
the  component  parts 
of  the  ovipositor  of 
a  longhorned  grass- 
h()l)per,  we  can  not 
fail  to  be  struck  at 
once  by  the  great  similarity  between  this  organ  and  the  sting  of 
the  bee  (fig.  ))(>).  The  first  gonai)ophyses  (JO)  of  the  ovipositor  are 
identical  with  the  lancets  {Lrt)  of  the  sting, and  their  sliding  connec- 
tion, by  means  of  longitudinal  trades,  with  the  second  g()nai)()i)hvses 
iJ(^r)  suggests  at  once  that  the  latter  represent  the  sheath  of  the 
sting  {ShS).  The  identity  is  si  ill  more  strongly  suggested  when  we 
observe  the  small  bulb  (^7//>)  formed  by  the  fV.sed  b;ises  of  th(\s(^ 
gonapophyses.  The  third  goiiapopliyses  (-jfr).  which  inclose  biMw(HMi 
ihcm  the  other  parts  of  (he  ovipositor.  repri»sent  the  pali)i  of  the 
sting  {SfnPt/)).  If.  finally,  wc  study  the  dcNclopment  of  the  i)arts  of 
tlic  sting  we  arc  cominccd  that  this  siniihii'ity  b:'t\vccn  the  sting  ami 
an  oN'ipositor  nican>  something  more  than  an  accidental  rcscmUlance  ; 


Fi( 


-Ventral  viow  of  stinj;  of  worker  and  accessory  parts, 
flattened  out. 


THE   ABDOMEN,    WAX    GLANDS,   AND   STING.  77 

between  two  different  ()r<j:ans — in  fact  wc  can  not  (loiil)t  tliat  the  sting 
is  simply  an  ovipositor  which,  being  no  longer  needed  for  egg-hiying 
purposes,  has  been  modified  into  a  poison-injecting  aj)paratus.  Zan- 
der (1899,  1900)  and  others  have  shown  that  tlie  sting  of  the  bee 
arises  from  six  little  abdominal  processes  of  the  larva,  two  of  wliich 
arise  on  the  eighth  segment  and  four  on  the  ninth.  Those  of  the  first 
pair  develop  into  the  lancets,  those  of  the  middle  pair  on  the  ninth 
segment  fuse  to  form  the  sheath,  while  those  of  the  outer  pair  be- 
come the  palpi.  The  ovipositor,  it  will  be  remembered,  develops  in 
the  lower  insects  from  two  pairs  of  processes  arising  on  the  eighth 
and  ninth  abdominal  sterna,  the  second  pair  of  which  very  soon 
splits  into  four  processes.  The  simultaneous  appearance  of  six  on 
the  bee  larva  is  simply  an  example  of  the  hurrying  process  or  accelera- 
tion that  the  embryos  and  young  of  most  higher  forms  exhibit  in 
their  development. 

It  is  only  the  higher  members  of  the  Hymenoptera,  such  as  the 
wasps  and  the  bees  and  their  close  relatives,  that  possess  a  true  sting. 
The  females  of  the  lower  members  have  ovipositors  which  closely  re- 
semble those  of  such  insects  as  the  katydids,  crickets,  and  cicadas,  but 
which,  at  the  same  time,  are  unquestionably  the  same  as  the  sting  of 
the  stinging  Hymenoptera.  It  is  said  that  the  queen  bee  makes  use 
of  her  sting  in  placing  her  eggs  in  the  cells,  but  both  the  wasps  and 
the  bees  deposit  their  eggs  in  cells  or  cavities  that  are  large  enough  to 
admit  the  entire  abdomen,  and  so  they  have  but  little  use  for  an  egg- 
placing  instrument.  But  the  females  of  the  katydids  and  related 
forms  like  Conocephalus  (fig.  8)  use  their  ovipositors  for  making  a 
slit  in  the  bark  of  a  twig  and  for  pushing  their  eggs  into  this  cavity. 
The  cicada  and  the  sawfiy  do  the  same  thing,  while  the  parasitic 
Hymenoptera  often  have  extremely  long  and  slender  piercing  oviposi- 
tors for  inserting  their  eggs  into  the  living  bodies  of  other  insects. 

An  examination  of  the  sting  in  place  within  the  sting  chamber,  as 
shown  by  figure  41,  will  suggest  what  the  accessory  plates  represent  in 
other  less  modified  insects.  It  has  already  been  explained  that  the  last 
external  segment  of  the  female  abdomen  (fig.  32,  VII)  is  the  seventh. 
Within  the  dorsal  part  of  the  sting  chamber  is  a  slight  suggestion  of 
the  eighth  tergum  (fig.  41,  VIIIT),  which  laterally  is  chitinized  as  a 
conspicuous  plate  bearing  the  last  or  eighth  abdominal  spiracle  {Sjy). 
The  triangular  plate  {Tri)^  as  Zander  has  shown  by  a  study  of  its 
development,  is  a  remnant  of  the  eighth  sternum,  and  the  fact  that  it 
carries  the  lancet  {Let)  shows  that  even  in  the  adult  this  appendage 
belongs  to  the  eighth  segment.  The  quadrate  plate  {Qd)^  since  it  is 
overlapped  by  the  spiracle  plates  of  the  eighth  tergum,  might  appear 
to  belong  to  the  eighth  sternum,  but  Zander  has  shown  that,  by  its 
development,  it  is  a  part  of  the  ninth  tergum.  In  many  other  adult 
Hymenoptera,  mureuver,  the  quadrate  plates  are  undoubtedly  tergal. 


78  THE  ANATOMY  OF  THE  HONEY  BEE. 

for  they  are  sometimes  connected  by  a  bridge  behind  the  eighth 
tergum.  The  oblong  phite  {Oh)  and  its  stalk  represent  the  ninth 
sternum,  and  since  it  carries  both  the  arm  of  the  sheath  {ShA)  and 
the  palpus  {Pip)  it  still  maintains  its  original  relationships  to  the 
gonapophyses.  The  membranous  lobe  arising  from  between  the 
oblong  plates  and  overlapping  the  bulb  of  the  sting  (figs.  36  and  37, 
IXS)  must  belong  to  the  median  part  of  the  ninth  sternum. 

The  tenth  segment  (fig.  41,  X)  consists  of  a  short,  thick  tube  having 
the  anus  {Aii)  at  its  tip.  It  takes  no  part  in  the  formation  of  the 
sting,  but  is  entirely  inclosed  in  the  dorsal  part  of  the  sting  chamber 
beneath  the  seventh  tergum. 

In  the  accessory  plates  of  the  bee's  sting  we  have  a  most  excellent 
illustration  of  how  the  parts  of  a  segment  may  become  modified  to 
meet  the  requirements  of  a  special  function,  and  also  an  example 
of  how  nature  is  ever  reluctant  to  create  any  new  organ,  preferring 
rather  to  make  over  some  already  existing  structure  into  something 
that  will  serve  a  new  purpose. 

There  are  four  glands  connected  with  the  sting,  two  of  which 
are  known  to  secrete  the  poison,  which  is  forced  through  the  canal 
between  the  sheath  and  the  lancets  and  ejected  into  the  wound  made 
by  the  latter.  It  is  this  poison  that  causes  the  pain  and  inflammation 
in  the  wound  from  a  bee's  sting,  Avhich  would  never  result  from  a 
mere  puncture.  The  other  two  glands  have  been  described  as  ''  lubri- 
cating glands,"  being  supposed  to  secrete  a  liquid  which  keeps  the 
parts  of  the  sting  mechanism  free  from  friction.  They  lie  within 
the  body  cavity,  one  on  each  side  against  the  upper  edge  of  the 
quadrate  plate,  where  they  are  easily  seen  in  an  extracted  sting,  each 
being  a  small  oblong  or  ovate  whitish  cellular  mass.  Transverse 
microtome  sections  through  this  region  show  that  each  of  these 
glands  opens  into  a  pouch  of  the  membrane  between  the  quadrate 
plate  and  the  spiracle-bearing  plate  of  the  eighth  tergum.  Each 
gland  cell  communicates  with  this  pouch  by  a  delicate  individual 
duct.  The  secretion  of  the  glands  is  thus  poured  upon  the  outer  sur- 
faces of  the  (piadrate  plates  and  might  easily  run  down  ui)on  the 
bases  of  the  lancets  and  the  arms  of  the  sheath,  but,  for  all  that,  the 
notion  that  it  is  lubricative  in  function  is  probably  entirely  conjectural. 

The  large,  consi)icuous  jxjison  sac  (figs.  3(),  37,  41,  and  r)7,  Ps/tSc) 
that  o])ens  by  a  narrow  neck  into  the  anterior  end  of  the  bulb  of  the 
sting  is  Avell  known  to  everyone  at  all  acquainted  with  bees.  The 
l)oison  which  it  contains  comes  from  the  delicate  branched  thread 
attached  to  its  anterior  end  (fig.  57),  a  minute  tube  which,  if  traced 
forward  a  short  distance  from  the.  sac,  will  be  seen  to  divide  into  two 
branches,  which  are  h>ng  and  much  coiled  and  convoluted,  each  ter- 
minating finally  in  a  small  oval  enlargement  {AOl).  These  terminal 
swellings  are  generally  regarded  as  the  true  glands  and  the  tubes 


THE    ABDOMKN,    WAX    CLAXDS,    AND    STINCJ. 


79 


-^  v'"lnr 


Fig.  38.  —  Section  of 
small  piece  of  wall  of 
poison  sac  of  sting. 


.^-Lum 


{AOID)  as  tlioir  ducts,  l)iit  the  cpitlu'liiiin  of  tlic  liilx's  appears  to  he 

of  a  secretory  nature  also.  and.  if  it  is  not.  it  is  hard  to  see  any  reason 

for   their   o-reat    length.      Tt    also   does   not    look 

jorobable   that    the    two    little    end    bodies    could 

form  all  the  poison  that  fills  the  coin})aratively 

enormous  sac. 

The  Avails  of  the  poison  sac  (fig.  38)  are  lined 

by  a  thick  coat  of  laminated  chitin  {Int)  thrown 

into  numerous  high  folds.     In  the  neck  i)art  of 

the  sac  the  folds  are  arranged  very  regularly  in 

a    transverse    direction    and    form    interrupted 

chitinous  rings,  holding  the  neck  rigidly  open. 

The   epithelium    {K ptli)    contains   nuclei    (.V//). 

but  the  cell  boundaries  are  very  slightly  marked. 

There  is  a  distinct  basement  membrane    (/>J/), 

forming  a  tunica   propria   externally,  but  there 

are  no  muscle  fibers  of  any  sort  present  except 

a  few  which  are  inserted  upon  the  sac  from  some  of  the  surrounding 

organs  and  which  apparently  act  as  suspensoria. 

The  poison  found  in  the  sac  has  an 
acid  reaction  and  is  supposed  to  consist 
principally  of  formic  acid.  Hence  its 
gland  is  known  as  the  acid  gland  {AGl) 
of  the  sting. 

The  other  sting  gland  is  a  short,  very 
inconspicuous,  and  slightly  convoluted 
whitish  tube  (figs.  36,  37,  41,  and  57, 
BGl)  opening  directly  into  the  base  of 
the  bulb  ventrad  to  the  opening  of  the 
poison  sac.  Its  walls  consist  of  a  thick 
epithelium  of  distinct  cells  (fig.  39, 
Eptli)  lined  Avith  a  thin  chitinous  in- 
tima  {hit)  and  surrounded  by  a  distinct 
basement  membrane  {BM)^  but,  as  in 
the  other  gland,  there  are  no  muscles 
present.  The  secretion  of  this  gland  is 
said  to  be  alkaline  and  the  gland  is 
therefore  known  as  the  alkaline  gland 
{BGl)  of  the  sting. 

Experiments  made  by  Carlet  (1890) 
show  that  it  is  only  the  mixture  of  the 
products   from   the   tAvo   poison   glands 

that  is  fully  efi'ective  in  stinging  properties.    Carlet 's  experiments  Avere 

made  upon  houseflies  and  bloAvflie.-.    He  shoAvs  (1)  that  flies  stung  by  a 

bee  die  almost  instantly,  (2)  flies  artificially  inoculated  Avitli  the  secre- 


BM- 


Epth 


Fig.  39. 


-Sections  of  alkaline  gland 
of  sting. 


80  THE  AXATOMY  OF  THE  HONEY  BEE. 

tion  of  either  gland  alone  do  not  die  for  a  long  time  even  in  spite  of 
the  necessary  mutilation,  while  (3)  successive  inoculations  of  the 
same  fly  first  from  one  gland  and  then  from  the  other  produce  death 
in  a  much  shorter  time  than  when  inoculated  from  one  gland  alone — 
presumably  as  soon  as  the  two  liquids  mix  within  the  body. 

The  two  secretions,  one  acid  and  the  other  alkaline,  are  poured 
toofether  into  the  base  of  the  stino'  bulb  and  mix  within  the  cavity 
of  the  latter.  The  resulting  poison  is  then  driven  through  the  chan- 
nel in  the  shaft  to  near  the  tip  of  the  latter,  where  it  makes  its  exit 
into  the  wound.  Since  the  large  poison  sac  is  not  muscular,  the  poison 
is  not  forced  through  the  sting  by  it,  as  is  often  supposed.  A  glance 
at  figure  57  (see  p.  135)  will  show  that  the  accessory  plates  of  the  sting 
support  several  very  compact  sets  of  muscles  on  their  inner  faces. 
These  muscles  so  act  during  the  process  of  stinging  that  the  triangular 
plates  (figs.  3()  and  37.  Ti't)  turn  upon  their  hinge-joint  articulations 
with  the  oblong  plates  {Oh).  By  this  motion  of  the  triangular 
plates  the  attached  lancets  (Let)  are  moved  back  and  forth  along 
the  tracks  on  the  lower  edges  of  the  sheath  and  its  arms  {ShA). 
Each  of  these  tracks  consists  of  a  ridge  with  a  constricted  base  which 
dovetails  into  a  correspondingly  shaped  groove  on  the  dorsal  surface 
of  the  lancet.  This  structure,  as  seen  in  cross  sections  through  the 
shaft  and  bulb  of  the  sting,  is  shown  by  fig.  40  A,  B,  and  C.  The 
lancets  are  thus  held  firmly  in  place,  while  at  the  same  time  they  may 
slide  back  and  forth  with  perfect  freedom.  The  figures  show  also 
that  all  three  parts  of  the  sting  are  hollow,  each  containing  a  pro- 
longation {he)  of  the  bod}^  cavity.  Between  them,  however,  is  in- 
closed another  cavity  through  which  the  poison  flows.  This  is  the 
poison  canal  {PsnC).  In  the  bulb  (fig.  40  C)  the  body  cavity  is 
reduced  to  a  narrow  cleft  {he)  by  the  great  size  of  the  invaginated 
l)oison  canal  {PrsnC). 

It  will  now  be  most  convenient  to  describe  the  apparatus  by  means 
of  which  the  poison  is  ejected  from  the  sting.  As  before  pointed  out, 
the  large  poison  sac  can  have  no  functions  in  this  connection  because 
its  walls  are  entirely  devoid  of  muscle  fibers.  On  the  other  hand, 
there  is  an  actual  pumping  apparatus  situated  within  the  bulb.  This 
consists  of  two  ponchlike  lobes,  having  their  concavities  directed 
posteriorly,  atlached  to  the  upi)er  edges  of  the  lancets  {W^i.  40  I)  and 
(t,  VJr)  on  the  anterior  ends  of  the  parts  of  the  latter  which  slide 
within  the  lowei-  edges  of  the  bulb  chamber.  The  lobes  lie  side  by 
side  within  the  bulb  (fig.  40  C,  T7/'),  when  the  lancets  are  in  the  same 
])()siti()n,  and  each  has  an  accessory  lamina  against  its  own  inner  wall. 
When  the  lancets  are  })ushed  backward  the  walls  of  the  lobes  flare 
apai't  against  the  ])()ison  contained  in  the  bulb  and  drive  this  liquid 
before  them  into  the  channel  of  the  shaft,  while  at  the  same  time  they 
suck  more  j)ois<)n  into  the  front  of  the  bulb  from  the  glands.     When, 


THE    ABDOMEN,    WAX    GLANDS,    AND    STIN(i. 


81 


PinC-, 


PinC 


oi^  the  other  hand,  the  hincets  are  retracted  the  j)()uclie.s  colhipse  so 
that  they  may  be  drawn  back  through  the  poison-filled  bidb  without 
resistance,  hut  they  are  ready  for  action  again  as  soon  as  the  move- 
ment of  the  lancets  is  reversed.  The  whole  apparatus  thus  consti- 
tutes an  actual  force  pump  in  which  the  lolx^s  on  the  lancets  alter- 
nately act  as  a  piston  and  as  valves.  The  lancets  need  not  work 
together;  in  fact, 
they  more  often 
perhaps  work  al- 
ternately, the  lobes 
being  of  such  a 
size  as  to  be  ef- 
fective either  when 
acting  together  or 
separately. 

The  reader  ac- 
quainted with 
other  Avorks  on 
the  anatomy  of 
the  bee,  such  as 
those  of  Cheshire 
(1886),  Cook 
(1901),  Cowan 
(1001),  and  Arn- 
hart  (190G).  will 
see  often  repeated 
the  statement  that 
the  poison  leaves 
the  stinxr  both  bv 
a  ventral  opening 
between  the  lan- 
cets near  their  tips 
and  by  several  lat- 
eral i^ores  near  the 
ends  of  the  lancets 
opening  from  the 
poison  canal  upon 
the  bases  of  the  barbs.  The  writer,  however,  has  never  been  able 
to  observe  the  exit  of  the  poison  from  any  such  lateral  pores,  while, 
on  the  other  hand,  it  is  very  easy  to  watch  it  exude  from  between 
the  lancets  on  the  ventral  side  of  the  sting  near  the  tip.  If  an 
excited  bee  is  held  beneath  a  microscope  and  the  tip  of  the  sting 
observed,  the  poison  Avill  be  seen  to  accumulate  in  little  drops  near 
the  tip  on  the  ventral  side.  If,  also,  the  bulb  of  an  extracted  sting 
22181— No.  18—10 6 


Fig.  40.- 


A,  section  through  tip  of 


Details  of  sting  of  worker 
sting  showing  lancets  {Let)  and  shaft  of  sheath  (ShS)  sur- 
rounding central  poison  canal  {PsnC),  and  each  containing 
a  prolongation  of  the  body-cavity  (be)  ;  B,  section  of  same 
near  base  of  bulb  ;  C,  section  of  sting  through  basal  bulb, 
showing  poison  canal  as  large  invaginated  cavity  (PsnC) 
in  bulb  of  sheath  (ShB)  containing  the  two  valves  (Vlv) 
of  lancets  (Let)  ;  D,  part  of  left  lancet  carrying  valve  (Vlv), 
dorsal  view ;  E,  tip  of  lancet  showing  pores  opening  on 
bases  of  barbs  (oo)  coming  from  body-cavity  (he)  of  lancet — 
not  from  poison  canal  ;  F,  dorsal  view  of  shaft  of  sheath 
showing  lateral  series  of  pores  (oo)  from  prolongation  of 
body-cavity  (be)  ;  G.  lateral  view  of  left  valve  and  part  of 
lancet. 


82 


THE    ANATOMY    OF    THE    HONEY    BEE. 


be  squeezed  gently  between  a  pair  of  forceps  the  poison  will  be  seen 
to  emerge  in  the  same  way.  In  fact,  it  can  be  actually  squirted  out 
by  a  sudden  compression  when  the  bulb  is  well  filled  with  poison,  but 
there  is  never  any  evidence  of  its  escape  through  the  sides. 

An  examination  of  the  end  of  each  lancet  does  reveal  a  number  of 
oblique  pores  (fig.  40  E,  oo)  which  have  been  figured  by  other  writ- 
ers, and  they  certainly  open  on  the  bases  of  the  barbs  as  described, 
but  their  inner  ends  apparently  communicate  with  the  body  cavity 
(be)  of  the  lancet  instead  of  passing  clear  through  the  lancet  and 
opening  into  the  poison  canal.  Furthermore,  a  paired  series  of 
exactly  similar  pores  extends  the  entire  length  of  the  shaft  of  the 
sheath  (fig.  40  F,  oo),  opening  on  its  dorsal  surface  from  the  body 
cavity   (he).     No  one  could  possibly  claim  that  the  })oison  emerges 


Tri     Ob 

Fir;.  41.— Tip  of  nbdnmon  of  worker  witli  loft  sido  ivunovod.  showini;  li.irht  halves  of  sev- 
enth tei-Kum  (VIIT)  and  sternum  (VIIS),  containing;  the  stinjr  chamber  (A-A:)  cut  open 
alouK  the  line  bir,  exposing  the  eifihth  tersum  iVIlIT),  the  rudimentary  tenth  segment 
(X)  carrying;  the  anus  (-1»),  and  the  sitiuy  and  accessory  parts  slu)\vn  by  (iir.  oO. 

also  through  these  pores,  which,  very  curiously,  do  not  appear  to 
have  been  described  before,  although  they  are  even  more  conspicuous 
as  well  as  more  numerous  than  those  of  the  lancets.  The  writer  has 
not  been  successful  in  preparing  histological  sections  of  the  sting 
which  show  these  pores,  but  they  i)r()bably  constitute  the  ducts  of 
some  kind  of  subcuticular  glands. 

A  cross-section  through  the  sting  a  short  distance  in  front  of  its 
tij)  shows  that  the  lancets  are  here  separated  by  a  narrow  cleft  (fig. 
40  A),  while  elsewhei'e  (B  and  C)  they  are  contiguous.  This  cleft 
between  (lie  ends  of  the  lancets  forms  the  exit  for  (he  [)()ison  from  the 
cliannel. 

I'lie  ^(ing  of  (lie  (|ii('('n  is  iniich  longer  (lian  (hM(  of  (he  worker 
and  is  more  solidly  a((a('lied  widiiii  (li 


^(iiig  chamber. 


Its  shaft  is  I 


THE   ABDOMEN,    WAX    (iLANDS,    AND    STIN(].  83 

strongly  decurved  beyond  the  bull).  The  iMiicets  huve  fewei-  mikI 
smaller  barbs  than  those  of  the  worker,  l)ii(  (he  I  wo  poison  «^dan(ls 
are  well  developed  (fig.  57,  AGl  and  lUH),  while  (lie  i)()is()n  sae 
{PsnSc)  is  especially  large. 

A  number  of  minute  nniceUular  glands  ojxmi  upon  the  interseg- 
mental membrane  between  the  seventh  and  eighth  terga  of  the  ab- 
domen. These  are  sometimes  called  the  glands  of  Nassanoff,  after 
their  discoverer.  Xassanoff  suggested  that  they  are  sweat  glands, 
while  Zoubareff  thought  that  they  form  small  drops  of  liquid  said 
to  be  excreted  by  bees  during  flight  derived  from  the  excess  of  water 
in  the  newdy  collected  nectar.  Their  finiction,  however,  has  been 
much  more  carefully  investigated  by  Sladen  (1902),  who  found  that 
they  are  scent  organs  producing  a  strong  odor  even  when  the  part 
of  the  back  to  which  they  are  attached  is  removed  from  the  rest 
of  the  abdomen.  He  furthermore  identified  this  smell  as  the  same 
that  bees  give  off  when  a  lot  of  them  are  shaken  from  a  frame  on 
the  ground  close  to  the  front  of  the  hive.  Under  such  circumstances 
also,  as  in  natural  swarming  or  during  the  first  flights  in  the  spring 
or  after  a  period  of  bad  weather,  bees  are  well  known  to  produce  a 
peculiar  sound  called  the  *'  joyful  hum."  Sladen  observed  that  this 
was  produced,  in  the  case  of  bees  shaken  before  the  hive,  by  those 
individuals  who  first  found  the  hive  entrance,  then  by  those  next  to 
them,  until  very  soon  all  the  others  were  informed  of  the  location 
of  the  entrance  and  proceeded  to  make  their  way  in.  Also,  when  a 
swarm  loses  sight  of  its  queen,  those -that  find  her  first  set  up  this 
"  joyful  hum  "  and  immediately  the  rest  of  the  swarm  is  attracted 
to  the  spot.  In  the  springtime  the  young  bees  seem  to  be  guided 
in  their  flights  by  this  same  hum  of  the  old  ones.  Sladen,  however, 
observing  the  odor  emitted  at  the  same  time,  thinks  that  this  and 
not  the  sound  is  the  real  means  of  information,  the  sound  being 
simply  incidental  to  the  special  movement  of  the  wings  produced 
for  the  purpose  of  blowing  the  odor  away  from  the  bod}^  He  argues 
that  we  have  no  evidence  of  an  acute  sense  of  hearing  in  bees,  while 
it  is  well  known  that  they  possess  a  delicate  sense  of  smell  located  on 
the  antenna?.  This  argument  certainly  seems  reasonable,  and  we 
may  at  least  accept  Sladen's  theory  as  the  best  explanation  of  the 
function  of  the  glands  of  Xassanoff. 


84  THE    ANATOMY    OF    THE    HONEY   BEE. 

VI.    THE  ALIMENTARY  CANAL  AND  ITS  GLANDS. 

1.    THE     GENERAL     PHYSIOLOGY     OF     DIGESTION,     ASSIMILATION,     AND 

EXCRETION. 

It  is  no  exaggeration  to  say  that  eating  is  the  most  important  thing 
that  any  animal  does  and  that  its  alimentary  canal  is  the  most  im- 
portant organ  it  possesses.  The  entire  system  suffers  when  there  is  a 
deficiency  in  the  food  supply  or  an  impairment  in  the  digestive  appa- 
ratus. Every  other  function  is  either  subservient  to  or  dependent 
upon  that  which  furnishes  nourishment  to  the  cells.  The  senses  of 
sight,  smell,  and  taste  are  all  more  or  less  concerned  in  the  acquisition 
of  food.  The  muscular  system  enables  the  animal  to  hunt  for  it,  to 
dig  for  it,  to  climb  for  it,  or  to  chase  living  prey  either  on  the  ground, 
in  the  water,  or  in  the  air,  and  to  kill,  tear,  and  chew  it  when  ob- 
tained. The  blood  is  the  servant  of  the  stomach,  for  its  entire  func- 
tion in  insects  is  to  carry  the  products  of  digestion  to  the  body  cells. 
The  heart  furnishes  the  motor  power  of  the  blood.  The  respiratory 
function  is  accessory  to  that  of  digestion,  inasmuch  as  it  furnishes  the 
oxygen  Avhich  unites  Avith  the  Avaste  materials  ejected  from  the  cells 
and  renders  them  capable  of  being  removed  from  the  blood.  This 
removal  is  accomplished  partly  by  the  respiratory  SA^stem  itself  and 
partly  by  special  excretory  organs.  Thus  Ave  see  that  the  sense  organs 
and  the  muscular  sA^stem  are  the  agents  that  cooperate  in  obtaining 
the  raw  food,  the  digestive  tract  is  the  kitchen  of  the  body  in  which 
the  food  is  prepared  for  use,  the  blood  is  the  Avaiter  that  distributes 
it,  while  the  respiratory  and  excretoiy  systems  are  the  refuse  gath- 
erers that  remove  waste  products.  The  nervous  system  holds  the  con- 
trolling i^oAver  over  all  these  organs.  It  regulates  them  in  the  per- 
formance of  their  duties  and  coordinates  their  actions  so  that  they 
all  Avork  together.  It  makes  a  unified  organism  out  of  Avhat  would 
otherAvise  be  simply  a  complex  mass  of  variously  specialized  cells. 

The  reproductive  function  alone  contributes  nothing  to  the  indi- 
vidual. In  fact,  the  production  of  spermatozoa  by  the  male  and  of 
eggs  by  the  female  and  the  nourishing  of  the  embryo  and  the  young 
create  a  demand  upon  all  the  other  organs  for  material  Avhich  is 
separated  from  the  individual  that  produces  it.  But  this  is  what  the 
organism  exists  for;  this  is  its  reason  for  being.  At  least  this  is 
Avhat  it  amounts  to  in  the  case  of  the  individual,  though  from  a  Avider 
philosophical  standpoint  the  real  truth  is  j)robably  just  the  rcA^erse, 
viz,  any  species,  exists  because  its  individuals  reproduce  themselves. 

The  Avriter  has  already  made  frequent  use  of  the  Avord  "  cell," 
assuming  that  tlie  reader  is  familiar  with  the  meaning  of  this  Avord 
as  used  in  anatomy  and  physiology.  The  entire  body  of  an  animal 
or  plant  is  made  up  of  cells  or  tlieir  products.  The  Avord,  hoAvever,  is 
misleading,  for  a  cell  is  not  u  small  sac  or  empty  space,  as  was  at 


THE   ALIMENTARY    CANAL   AND    ITS   CJLANDS. 


85 


Slnt^ 


Vent 


Fig.  42.— Alimentary  canal  of  worker  (Phij-Rect),  together  with  pharyngeal  glands  {IGD, 
and  salivary  glands  of  head  {2G1 )  and  of  thorax  [SGI),  as  seen  by  cutting  body  open 
from  above  and  pulling  the  ventriculus  (Vent)  out  to  left. 


g6  THE  ANATOMY  OF  THE  HONEY  BEE. 

first  supposed  from  the  study  of  plants,  but  is  a  little  protoplasmic 
body  or  corpuscle,  visible  only  under  the  microscope,  surrounded  by 
a  membranous  cell  Avail  and  containing  a  small  internal  body  called 
the  nucleus.  The  different  cells  of  the  body  are  specialized  in  groups 
to  do  some  one  particular  thing — the  salivary  cells  secrete  saliva,  the 
muscle  cells  contract,  the  excretory  cells  pick  out  waste  substances 
from  the  blood,  and  so  on.  But  this  specialization  does  not  signify 
that  each  cell  does  not  perform  its  own  vital  processes  in  addition  to 
its  specialty.  The  fact  that  it  remains  alive  and  works  means  that 
the  complex  chemical  components  of  its  body  substance  or  protoplasm 
are  constantly  being  reduced  to  simpler  compounds  which  are  ex- 
pelled, while  new  protoplasm  is  built  up  from  the  supply  of  food 
material  brought  by  the  blood.  This  double  process  of  destruction 
and  reconstruction  is  known  as  metaholism^  while  its  two  phases,  the 
breaking-down  jDrocess  and  the  building-up  process,  are  known  as 
katabolism  and  anabolism^  respectively. 

Now,  while  all  the  cells  of  the  body  must  have  nourishment,  none 
of  them,  except  those  of  the  alimentary  canal,  is  capable  of  utiliz- 
ing the  raw  food  materials  that  an  animal  obtains  in  a  state  of  nature. 
These  materials  nuist  therefore  be  changed  into  some  other  form  in 
order  that  they  may  h^  assimilated  by  the  cells.  This  change  is  called 
digestion. 

The  single  cell  composing  the  body  of  a  Protozoan,  living  free  in 
nature,  digests  its  OAvn  food  and  then  assimilates  the  products  of  its 
own  digestion.  But,  of  the  cells  constituting  the  body  of  any  mul- 
ticellular animal,  only  those  of  the  alimentary  canal  are  capable  of 
digesting  raw  foodstuffs,  and,  moreover,  as  digestion  is  the  specialty 
of  these  cells,  they  have  also  to  digest  the  food  for  all  the  other  cells 
of  the  body. 

The  two  most  important  changes  that  must  be  brought  about  in 
the  natural  food  by  digestion  are  those  which  make  it  soluble  in  the 
})l()()d  and  which  render  it  capable  of  passing  through  animal  tissues. 
Ill  the  lirst  place,  the  food  must  diffuse  through  the  walls  of  the 
alimentary  canal  as  a  liquid  Avhich  mixes  with  the  blood,  for  there 
ai'e  no  pores  or  openings  of  any  sort  from  the  alimentary  canal  into 
the  body  cavity;  and  in  the  second  place,  it  must  pass  through  the 
f  the  cells  themselves.    The  digestive  changes  result  chiefly  in 

breaking  down  of  the  complex  molecules  of  the  raw  food  materials 
into  more  siiii])le  chemical  substances.  These  are  taken  up  by  the 
cells  and  reconstructed  into  complex  protoi)lasmi('  molecukvs  which 
can  not  escape  thiough  the  cell  membrane  until  they  are  again  broken 
down  into  simpler  forms. 

The  waste  products  of  the  cells  consist  principally  of  carbon,  hy- 
drogen, and  nitrogen.  These  are  converted  by  the  oxygen  supplied 
by  tiie  respiratory  system  into  (uirbon  dioxid,  water,  and  compounds  of 


wans  o 
a 


THE    ALIMENTARY    CANAL    AND    ITS    (iLANDS.  87 

urea.  Tlie  first,  hviufr  a  o;as,  mixes  witli  tlic  aii-  in  the  (raclicMl  lubes 
and  so  reaches  the  extei'ior  (hirino-  exhalation.  Miicli  of  the;  water  is 
also  given  off  through  (he  tracheal  system  in  the  form  of  vapor  which 
exhales  from  the  spiracles,  but,  since  insects  are  covered  by  their 
hard  chitinous  shell,  it  is  probable  that  they  do  not  ''sweat.*'  The 
compounds  of  urea,  and  probably  also  some  water,  are  separated 
from  the  blood  by  the  excretoi-y  glands,  caded  Malpighian  tubules 
in  insects,  which  empty  their  products  back  into  the  alimentary 
canal,  whence  they  are  discharged  with  the  ficces  from  the  intestine. 

Digestion  is  brought  about  by  substances  called  enzymes  which  are 
contained  in  the  various  liquids  mixed  with  the  food  in  the  alimentary 
canal.  These  liquids  are  secreted  by  the  salivary  glands  and  by  the 
cellular  walls  of  the  stonnich. 

2.    THE    SALIVARY    GLANDS. 

The  opening  of  the  salivary  duct  on  the  base  of  the  proboscis  has 
already  been  described  (see  pp.  49-51).  The  true  salivary  glands,  or 
those  corresponding  with  the  salivary  glands  of  other  insects,  are 
arranged  in  two  pairs,  one  situated  within  the  head  (figs.  19  and  42, 
2GI)  and  the  other  Avithin  the  thorax  (fig.  42,  3GI).  The  four  ducts 
unite  into  one  median  tube,  which  enters  the  base  of  the  labium  (fig. 
19,  SalD)  and  opens  upon  the  upper  surface  of  the  ligula  (fig.  15  F, 
and  fig.  1().  ^SaJDO).  The  large  and  conspicuous  glands  lying  within 
the  anterior  and  upper  parts  of  the  head  and  opening  into  the 
])harynx  will  be  described  later  in  connection  with  this  organ.  They 
are  special  pharyngeal  glands  in  no  way  homologous  with  the  salivary 
glands  of  other  insects,  and  are  by  many  supposed  to  secrete  the 
brood  food  instead  of  a  digestive  liquid  like  saliva. 

The  salivary  glands  of  the  head  {System  No.  2  of  Cheshire,  post- 
cerehral  glands  of  Bordas)  lie  against  the  posterior  walls  of  the 
cranium.  In  the  worker  each  consists  of  a  loosely  arranged  mass  of 
pear-shaped  follicles  or  acini  whose  individual  ducts  unite  irregu- 
larly with  one  another  and  eventuallv  form  a  common  duct  on  each 
side  (figs.  19,  42,  and  43  F,  2GI).  Their  two  ducts  unite  with  the 
median  duct  from  the  thoracic  glands  just  before  the  bases  of  the 
mesocephalic  pillars  (fig.  19).  In  the  drone  these  glands  have  a 
quite  different  appearance  from  those  of  the  female,  each  consisting 
of  a  compact  mass  of  very  small  follicles  connected  by  minute  ducts 
and  flattened  against  the  posterior  walls  of  the  head  (fig.  43  B  and  C, 
2GI).  A  large  lobe  of  this  gland  in  the  drone  extends  forward  on 
each  side  against  the  face,  between  the  compound  eye  and  the  clypeus 
(fig.  10  C,  2Gl)^  thus  occupying  the  position  of  the  large  mandibular 
gland  in  the  worker  (A,  IMdGl)  and  in  the  queen  (B,  IMdGl). 
There  is  also  a  prominent  triangular  mass  of  glandular  cells  in  the 
drone  situated  just  above  the  ocelli  (fig.  10  C,  2GI)  which  has  been 


88 


THE   ANATOMY    OF   THE    HONEY   BEE. 


described  by  Bordas  (1895)  as  a  separate  gland  opening  by  two  ducts 
into  the  oesophagus  just  behind  the  pharynx.  The  writer,  however, 
has  been  utterly  unable  to  discover  an}^  such  ducts,  though  two  sus- 
pensorial  ligaments  of  the  anterior  end  of  the  oesophagus  are  at- 
tached to  the  wall  of  the  head  at  the  posterior  ends  of  these  glands 
(fig.  11  B,  ^)  and  might  easily  be  mistaken  for  ducts.  These  "  post- 
ocellar  glands  "  of  Bordas,  moreover,  appear  to  be  simply  detached 
lobes  of  the  postcerebral  glands.  They  are  prominent  also  in  the 
queen  (fig.  10  B,  2GI)  and  are  represented  by  a  few  follicles  in  the 
worker. 


■^^  '^^ 


Fig.  43. — A,  small  piece  of  large  lateral  pharyngeal  glands  in  head  of  worker ;  B,  piece  of 
postcerebral  salivary  glands  in  head  of  drone  ;  C,  postcerebral  glands  {2GI)  in  normal 
position  against  posterior  wall  of  head  in  drone  ;  D,  pharyngeal  plate  (s)  of  worker, 
ventral  view,  showing  bases  of  lateral  pharyngeal  glands  {IGD  and  their  receptacula 
(mm),  and  median  ventral  pharyngeal  gland  (-J0?)  ;  E.  corresponding  view  of  phai-yngeal 
plate  of  drone,  showing  entire  absence  of  lateral  pharyngeal  glands,  and  greater  devel- 
opment of  small  median  glands  (^Cr?>  ;  F,  part  of  postcerebral  gland  of  worker. 

Bordas  describes  the  follicles  of  the  postcerebral  glands  in  the 
worker  as  hollow  sacs,  each  having  a  large  lumen  lined  with  a  chiti- 
nous  intima.  Their  secretion,  he  says,  is  a  thin  viscid  liquid,  pale 
yellow  in  color  and  having  a  slightly  alkaline  reaction.  According  to 
Schiomenz  (1888)  each  gland  is  developed  as  an  outgrowth  from  the 
common  duct  of  the  thoracic  ghmds. 

The  salivary  glands  of  the  thorax  in  the  bee  {System  No.  3  of 
Cheshii'e,  tliordclc  sdlirun/  (/lands  of  Bordas)  are  the  ones  that  cor- 
respond with  tlu'  ordinary  salivary  glands  of  other  insects.  They 
are  described  by  Schiemenz   (1883)    as  being  formed  inside  of  the 


THE   ALIMENTARY    CANAL   AND   ITS   CLANDS.  89 

outer  covering  (tunica  propria)  of  the  first  part  of  tlie  larval  silk 
glands.  But  it  is  of  common  occurrence  in  insects  that  the  salivary 
glands  are  temporarily  specialized  as  silk-producing  organs  in  the 
larva.  In  the  adult  worker  these  glands  lie  in  the  ventral  part  of 
the  anterior  half  of  the  thorax  (fig.  42,  SGI).  The  two  are  widely 
separated  anteriorly,  but  their  posterior  ends  are  contiguous.  P2ach 
consists  of  a  mass  of  small,  many-branched,  glandular  tubes  o})ening 
into  several  collecting  ducts  which  empty  into  a  sac  near  the  ante- 
rior end  of  the  gland  {II) .  From  each  of  these  reservoirs,  then,  a  duct 
{Dct)  runs  forward  and  fuses  with  the  one  from  the  opposite  side 
just  within  the  foramen  magnum  of  the  head.  The  common  duct 
thus  formed  turns  dow^nward  within  the;  head,  receiving  the  two  ducts 
of  the  post  cerebral  salivary  glands  and  then  enters  the  base  of  the 
mentum  (figs.  19  and  43  C.  SaJD).  to  open  as  already  described  on  the 
upper  side  of  the  ligula  at  the  root  of  the  glossa  and  between  the 
bases  of  the  tAvo  paraglossa?  (fig.  15  F  and  16,  SalDO).  The 
secretion  of  the  thoracic  glands  is  said  also  to  be  weakly  alkaline. 
Therefore  the  entire  salivary  fluid  poured  out  upon  the  labium  is 
alkaline,  and  it  must  be  designed  to  act  especially  upon  the  food 
taken  through  the  proboscis.  This  action,  furthermore,  on  account  of 
the  location  of  the  salivary  opening,  may  take  place  before  the  food 
enters  the  mouth. 

The  food  of  the  bee  consists  normally  of  pollen,  nectar,  and  honey. 
The  first  is  eaten  entirely  with  the  mandibles,  while  the  other  two  are 
taken  through  the  proboscis.  The  pollen  is  to  the  diet  of  the  bee  what 
meat  is  to  ours;  that  is  to  say,  it  contains  the  proteid  or  nitrogen- 
containing  ingredient  of  the  food  which  is  necessary  to  the  sup- 
port of  any  animal,  and  also  substances  comparable  with  fat,  called 
in  general  hydrocarhons.  The  nectar  and  honey  consist  principally 
of  grape  sugar,  fruit  sugar,  and  cane  sugar,  which  belong  to  the  class 
of  chemical  substances  known  as  carbohydrates.  Now,  all  of  these 
foodstuffs,  except  the  grape  and  fruit  sugars,  have  to  be  changed 
chemically  by  the  digestive  process  before  they  can  be  absorbed  into 
the  blood.  The  pollen,  which  contains  the  proteids  and  hydrocarbons 
of  the  food,  is  taken  directly  into  the  mouth  by  means  of  the  man- 
dibles and  apparently  is  not  digested  until  it  reaches  the  small  in- 
testine, and  therefore  it  would  seem  that  it  is  the  cane  sugar  which 
must  be  affected  by  the  saliva.  The  change,  or  inversion,  as  it  is 
called,  of  cane  sugar,  which  has  a  very  large  molecule  (CioHooO^J, 
consists  of  its  reduction  to  grape  and  fruit  sugars  which  have  smaller 
molecules  {CJ^xfio)-  Starch  (CgHioO-)  must  also  be  reduced  to 
simpler  and  more  soluble  compounds  before  it  is  capable  of  absorp- 
tion. Its  inversion  is  effected  in  us  partly  by  the  saliva,  but  starch 
appears  to  form  a  very  inconsiderable  element  in  the  bee's  diet. 


90  THE   ANATOMY   OF    THE    HONEY   BEE.  1 

3.    THE    ALIMENTARY    CANAL. 

The  alimentary  canal  is  a  tube  which  extends  through  the  entire 
length  of  the  body  and,  on  account  of  being  more  or  less  coiled,  it  is 
generally  considerably  longer  than  the  length  of  the  body  in  insects. 
It  has  no  openings  of  any  sort  into  the  body  cavity.  The  internal 
organs  are  packed  closely  about  it,  and  the  interstices  are  filled  with 
the  blood,  there  being  no  special  arteries  or  veins  in  insects.  The 
amount  of  space  occupied  by  the  alimentary  canal  varies  according  to 
the  amount  of  food  it  contains,  and  for  this  reason  it  seldom  looks 
exactly  alike  in  any  tAvo  individuals  examined. 

The  part  of  the  canal  immediately  following  the  mouth  forms  an 
enlargement  (fig.  42,  Phy)  called  the  pharynx.  Succeeding  this  is 
a  slender  tube  which  leaves  the  head  by  the  foramen  magnum  above 
the  small  transverse  tentorial  bar  and  traverses  the  entire  length 
of  the  thorax.  This  is  the  (t^sophagus  {(E).  In  the  anterior  part  of 
the  abdomen  the  oesophagus  expands  into  a  large  thin-walled  sac 
which  is  ordinarily  called  the  crop  or  inylurles^  but  which,  in  the 
bee,  is  known  as  the  honey  stomach  {IIS).  Behind  this  is  a  short, 
narrow,  necklike  division,  with  rigid  walls  constituting  the  /^?'<y- 
reritriofhis  {Prent).  Then  comes  a  large  U-shaped  part,  with  thick, 
spongy-looking  walls  containing  riumerous  annular  constrictions. 
This  is  the  ventriculns  {Vcnt)^  or  stomach,  of  the  bee,  frequently  re- 
ferred to  as  the  "  chyle  stomach."  Following  the  ventriculns  is  a 
short,  narrow,  coiled  nmall  inteMne  {Slut)  having  a  circle  of  about 
one  hundred  long,  greatly  coiled,  blind,  threadlike  tubes  opening  into 
its  anterior  end.  These  latter  are  called  the  Mai p'n/hian  tahutes 
{Mai).  Functionally  they  do  not  belong  to  the  digestive  tract,  since 
they  are  excretory  organs,  corresponding  with  the  nephridia  of  other 
invertebrates  and  with  the  kidneys  of  vertebrates.  Following  the 
small  intestine  is  the  larye  intestine^  or  rectum  {Rcct),  which  is  often 
distended  by  its  contents  into  a  great  sac  occupying  a  large  part  of 
the  abdominal  cavity.  Six  whitish  bands  on  its  anterior  end  are 
called  the  rectal  glands  {RGl).  The  rectum  opens  to  the  exterior 
through  the  anus,  which  is  situated,  as  already  described,  at  the  end  of 
{\\v  nidimentar}^  tenth  or  last  segment  of  the  abdomen  (fig.  41,  An). 

After  this  brief  general  survey  of  the  parts  of  the  alimentary 
canal,  we  shall  proceed  with  the  description  of  each  in  detail,  and  at 
the  same  time  give  what  is  known  of  the  role  each  ])lays  in  the 
process  oi  digestion.  What  is  known,  however,  about  digestion  in 
the  bee,  or  in  any  insect,  for  that  matter,  really  amounts  to  nothing, 
but  the  \'iews  of  Narious  writers  on  the  snbjcH't  must  be  discussed 
briefly,  in  order  to  show  how  little  has  actually  been  demonstrated. 

The  pharynx  (figs.  11  H,  li),  and  4'i,  Phy)  lies  in  the  anterior  part 
of   the    head    close    behind    the    clypeus,   extending    from    the    mouth 


THE    ALlMKNTAItV    CANAI.   AND    ITS    CJLANDS.  91 

dorsally  to  above  the  anteniur,  where  it  turns  posteriorly  and  con- 
tracts into  the  much  narrower  (josophagus  {(E).  Attached  to  its 
walls  are  numerous  suspensorial  muscles,  wdiose  contraction  nnist 
expand  the  pharyngeal  cavity,  while  the  latter  may  be  contracted 
by  the  sheet  of  muscles  surrounding  its  walls.  In  this  way  the 
pharynx  is  undoubtedly  able  to  i)erf()rm  a  sucking  action,  by  means 
of  which  the  liquid  foods  are  taken  into  the  mouth.  Its  lateral 
walls  are  strengthened  by  two  long,  chitinous  rods  (figs.  11  li  and 
19,  h)^  which  arise  from  a  median  anterior  plate  in  its  floor  (fig.  19, ,s'). 
The  anterior  end  of  this  plate  is  prolonged  into  two  free,  tapering 
lobes  wdiich  hang  down  over  the  lower  rim  of  the  mouth.  The  plate, 
in  the  Avorker,  and  the  bases  of  the  rods  are  shown  in  ventral  view, 
removed  from  the  pharyngeal  wall,  in  figure  43  D.  Near  Avhere  the 
rods  join  the  plate  are  two  long,  chitinous  pockets  (mm),  opening 
above,  which  receive  the  ducts  of  the  two  large  glands  {J 01)  lying 
within  the  anterior  part  of  the  head.  Between  these  two  pockets  is  a 
transverse  row  of  cells  {^Gl)^  which  have  been  described  by  Bordas 
(1895)  as  the  "sublingual  glands,"  bnt  this  name  is  not  appropriate 
in  insects,  for,  while  the  gland  in  question  may  be  suggestive  of  the 
sublingual  salivary  gland  of  Vertebrates,  it  does  not  lie  beneath  the 
tongue  or  lingua  of  the  bee.  Although  the  pharyngeal  plate  lies 
upon  the  floor  of  the  true  mouth,  it  is  not,  as  already  explained  (p. 
44),  the  equivalent  of  w^hat  is  properly  called  the  tongue,  lingua,  or 
hypopharynx  in  other  insects — this  organ  being  absent  in  most 
Hymenoptera.  The  only  suggestion  the  writer  can  make,  however, 
is  to  call  this  group  of  cells  the  ventral  or  median  nentral  pharyngeal 
gland  in  distinction  to  the  large  lateral  glands.  A  comparative  view 
of  the  pharyngeal  plate  and  its  accessory  parts  in  the  drone  is  given 
in  figure  43  E.  The  plate  itself  {s)  is  shorter  than  in  the  worker, 
and  its  anterior  lobes  are  smaller.  The  lateral  glands  and  their 
receptacula  are  entirely  absent,  but  the  median  glands  {IfGl)  are 
much  larger  than  those  of  the  worker.  Bordas  says  that  each  acinus 
of  the  latter  glands  in  both  the  worker  and  the  drone  is  provided 
with  a  fine,  sinuous  canaliculus,  and  that  these  tiny  ducts  open 
separately  in  two  bundles  on  the  lateral  parts  of  the  pharyngeal 
plate.  The  lateral  glands  are  present  in  the  queen,  but  are  very  small 
and  rudimentary. 

Especial  interest  attaches  to  the  large  lateral  pharyngeal  glands  of 
the  worker  {System  No.  1  of  Cheshire,  the  supracerehral  glands 
of  Bordas),  because  they  are  regarded  by  many  as  the  source  of  the 
brood  food  and  the  so-called  "  royal  jelly,"  which  is  fed  to  the  larvse 
and  to  the  adult  queens  and  drones  by  the  workers.  Each  consists 
of  a  long  coiled  string  of  small  ovate  follicles  attached  to  one  median 
duct  (fig.  43  A)  and  the  two  are  intricately  packed  into  the  anterior 
and  upper  parts  of  the  head  (figs.  10  A,  19,  and  42,  IGl),    Each 


92  THE   ANATOIMY   OF    THE    HONEY   BEE. 

acinus  consists  of  a  solid  mass  of  several  small  cells,  which  are  pene- 
trated by  a  large  number  of  fine,  chitinous  ducts,  arising  in  the  neck 
of  the  acinus  from  the  common  duct  of  the  gland.  These  follicular 
ducts  can  be  very  clearly  shown  by  treating  a  part  of  the  gland  with 
weak  caustic  potash,  which  dissolves  the  protoplasm  of  the  cells 
and  brings  out  the  bunch  of  ductules  very  clearh^ 

The  fact  that  these  glands  are  entirely  absent  in  the  drone  and  at 
best  rudimentary  in  the  queen  shows  that  they  must  in  some  way  be 
connected  with  the  special  functions  of  the  worker.  Schiemenz  (1883 ) 
and  Cheshire  (1886)  have  shown  that  their  development  in  the  dif- 
ferent species  of  bees  is  in  proportion  to  the  social  specialization. 
They  vary  from  a  group  of  cells  opening  by  separate  ducts  upon  the 
pharyngeal  plate  to  the  highly  developed  condition  they  present  in 
the  honey  bee.  The  writer  questions,  however,  whether  these  authors 
did  not  mistake  the  median  pharyngeal  glands  of  these  lower  genera 
of  bees  for  rudimentary  representatives  of  the  lateral  glands.  Bordas 
states  that  the  former  occur  in  all  Hymenoptera,  but  Schiemenz  and 
Cheshire  did  not  seem  to  recognize  them.  The  bumblebees  {Bomhiis) 
have  them  almost  as  well  developed  as  the  hone}^  bee  (Apis),  espe- 
ciall}^  the  large  females.  In  the  genus  Psi/thii us  they  are  similar  to 
those  of  BowJbus  but  are  smaller,  while  in  such  genera  as  Andrena 
and  Arithophora  they  are  rudimentary  or  consist  of  a  few  scattered 
cells.  Both  Schiemenz  and  Cheshire  have  thus  argued  strongly  that 
these  glands  of  the  pharynx  are  the  organs  that  produce  the  brood 
food.  On  the  other  hand,  Schonfeld  (1880)  has  made  an  equally 
strong  plea  in  favor  of  the  ventriculus  as  the  producer  of  this  impor- 
tant material.  He  believes  that  the  brood  food,  especially  roynl 
jelly,  is  regurgitated  chyle.  Both  Schchifeld  and  Cook  (1904)  fed 
bees  in  a  hive  some  honey  containing  powdered  charcoal  and  later 
found  this  in  the  brood  food  in  the  comb  cells,  thus  apparently  con- 
firming its  ventricular  origin.  However,  the  charcoal  that  got  into 
the  cells  might  have  come  from  the  mouth,  the  a^sophagus,  or  the 
honey  stomach.  It,  of  course,  could  not  have  gone  through  the 
stomach  walls  and  entered  the  pluuyngeal  glands,  as  proved  by  Dr. 
J.  A.  Nelson,  of  this  Bureau,  from  microtome  sections  of  bees  fed  on 
lampblack.  The  arguments,  then,  in  favoi'  of  the  stomach  and  the 
pharyngeal  glands  seem  eciually  strong,  and  ])erliaps  the  truth  is,  as 
occurs  in  so  many  such  cases,  that  both  sides  are  right — that  the  brood 
food  is  a  mixture  of  chyle  from  the  stomach  and  of  secretion  from 
the  phnryngeal  ghmds. 

Arnhart  (11)()(>)  seems  to  adopt  the  positicm  that  the  brood  food 
is  cliyle  which  has  })een  acid i (led  by  the  addition  of  an  acid  from  the 
ghiiids.  lie  states  llmt  the  acid  reaction  of  the  royal  jelly  is  due  to 
the  picscnct'  of  thi'cc- fourths  of  1  j)er  cent  of  tartaric  acid.  The 
contents  of  the  ventriculus,  on  the  other  hand,  and  for  that  matter 


THE   ALIMENTAHV    CANAL   AND    TI'S    (]I.ANI)S.  93 

of  all  the  parts  of  tho  aliinontarv  caiial.  arc  nlkalinc.  IIciicc,  it 
seems  very  loaical  to  suppose  that  if  the  hiood  food  coincs  from  the 
stomach,  its  acid  constituent  is  furnished  hy  the  glands  in  the  head. 
But  thfe  difference  between  the  brood  food  found  in  the  cells  and  the 
contents  of  the  ventriculus  is  so  great  that  it  would  seem  as  if  a  very 
substantial  addition  of  something  more  than  a  mere  i)reservative  acid 
must  be  made  to  the  latter. 

The  brood  food  given  to  the  queen  larva%  known  as  I'oyal  jell}-,  is  a 
gummy  paste  of  a  milky-white  color  when  fresh,  but  when  taken  out 
of  the  cell  it  soon  acquires  a  darker  tone  Avith  a  yellowish  tint.  Under 
the  microscope  it  appears  to  be  a  homogeneous,  very  minutely  granu- 
lar mass.  Tt  is  very  acrid  and  pungent  to  the  taste,  and  must  be 
strongl}^  acid.  Samples  examined  by  the  Avriter  taken  from  cells 
containing  queen  larva?  two  and  four  days  old  contained  a  number  of 
fresh  undigested  pollen  grains  but  no  bits  of  hairs  such  as  occur  in 
the  stomach. 

The  possible  ventricular  origin  of  a  part  of  the  brood  food  and  its 
regurgitation  will  be  further  discussed  Avhen  we  treat  of  the  stomach 
(page  98).  The  writer  does  not  advocate  any  personal  view^  regard- 
ing the  origin  of  this  larval  food — the  fact  is,  there  is  not  enough 
known  about  it  to  enable  one  to  formulate  any  opinion  worth  w^hile. 
We  know  only  that  the  whitish  paste  comes  out  of  the  mouths  of  the 
workers,  but  we  knoio  nothing  of  Avhere  it  is  made  or  of  how^  it  is 
made.     Hence  we  can  but  aAvait  the  evidence  of  further  investigation. 

The  brood  food  is  fed  to  the  larva'  by  the  workers  and  is  produced 
in  greatest  abundance  by  the  younger  individuals.  The  larva?  of  the 
queens  are  said  to  receive  nothing  but  pure  royal  jelly  throughout 
their  entire  developmental  period,  while  the  larvae  of  the  drones  and 
the  workers  are  given  the  pure  product  only  during  the  first  three 
days  of  their  life.  From  the  beginning  of  the  fourth  day  on,  honey 
is  said  to  be  mixed  with  the  diet  of  the  drones  and  workers  and,  in 
the  case  of  the  former,  undigested  pollen  also.  Moreover,  the  adult 
queens  and  the  drones  receive  a  certain  amount  of  prepared  food 
throughout  their  lives ;  if  they  do  not  get  it  they  become  weak.  While 
they  can  feed  themselves  with  honey  they  apparently  can  not  eat 
pollen,  and  consequently  are  not  able  to  obtain  the  proteid  element  of 
diet  unless  fed  this  in  a  predigested  condition  by  the  workers.  Dur- 
ing egg-laying  activity  the  queen  especially  demands  this  food,  and 
by  furnishing  or  withholding  it  the  workers  probably  have  the  power 
of  stimulating  or  inhibiting  her  production  of  eggs.  Arnhart  (1906) 
says  that  the  workers  feed  it  to  Aveak  or  starA^ed  members  of  their  OAvn 
class,  the  material  being  accumulated  upon  the  upper  surface  of  the 
mentum  of  one  bee  Avhence  it  is  sucked  up  through  the  proboscis  by 
the  other.  All  of  these  statements,  hoAvever,  concerning  the  feeding 
of  the  brood  and  the  differences  in  the  diet  need  to  be  A^erified.     They 


94 


THE    ANATOMY    OF    THE    HONEY   BEE. 


Pvent 


yent 


are  based  chiefly  on  the  work  of  Phmta,  published  in  1888.  Cheshire 
(188G)  states  that  the  stomachs  of  queens  contain  a  substance  which 
is  "  microscopically  indistinguishable  from  the  so-called  royal  jelly," 
scarcely  a  pollen  grain  being  discoyerable  in  it.  If  this  is  so,  if  would 
seem  to  proye  that  the  queen  is  fed  this  substance  by  the  worker,  for 
the  stomach  of  the  latter  is  inyariabh^  filled  with  a  dark-brown  slime 

containing  a  vary- 
ing amount  of  pol- 
len and  in  no  way 
resembling  royal 
jell}'.  Cheshire 
further  saj^s  that 
before  impregna- 
tion the  stomachs 
of  the  queens  al- 
ways contain  pol- 
len, the  ro3^al  jelly 
being  found  in 
them  two  or  three 
days  after  impreg- 
nation, when  all 
traces  of  pollen 
haye  disappeared. 

The  n  a  r  r  o  w 
oesophagus  (fig.  42, 
(L^)  is  a  simple  tube 
with  a  thick  chiti- 
nous  lining  and 
muscular  walls. 
The  epithelium  (fig. 
45)  is  yery  rudi- 
mentary, its  cell 
boundaries  being 
lost  and  its  nuclei 
(.V?/)  appearing  as 
if  imbedded  in  the 
lower  laj^ers  o.f  the 


rsC^t 


^^nt.g^^ 


Fig.  44. — A,  honey  stomach  (HS)  of  worker  with  posterior  end 
of  oesophagus  {(J'J),  provontriculus  (I'rcnt),  and  anterior 
end  of  vontriculiis  (]'cnt)  ;  I>.  same  of  queen:  (.',  lu)ni\v 
stomach  (//*S')  of  worker  mostly  cut  away  exposing  tlie 
stomach-mouth  (iin)  of  proventriculus  (I'vcnt)  leading;  info 
ventriculus  {Vent)  ;  I),  honey  stomach  of  drone. 


thick  transparent 
inliiiia  {Int).  The  nniscles  are  disposed  in  an  outer  layer  of  trans- 
verse fibers  {TM(i)  and  an  inner  layer  of  longitudinal  ernes  {LMcl). 
The  honey  stomach  (fig.  -I'J,  IIS)  is  simply  an  eidargement  of  the 
l)()steri()r  end  of  (lie  (rs()i)hagus  lying  witliin  the  anterior  part  of 
the  abdominal  cavity.  It  is  best  developed  in  th(^  worker  (fig.  44  A), 
but  is  present  also  in  the  (|ueen  (B)  and  in  the  drone  (D).  The 
organ  should  perhaps  have  been  named  the  nectar  stomach,  for  its 


THE   ALIMENTARY    CANAL   AND    ITS   (JLANDS.  95 

principal  function  in  the  bee  is  to  hold  the  nectar  as  it  is  collected 
from  the  flowers  and  to  allow  the  worker  to  accumulate  a  consider- 
able (inantity  of  this  li(]uid  before  ^oinf2^  back  to  the  liive.  Hence, 
since  the  honey  stomach  is  a  sac  with  very  distensible  walls,  its 
apparent  size  varies  greatly.  AVhen  empty  it  is  a  small  flabby  pouch, 
but  when  full  it  is  an  enormous  balloon-shaped  bag  with  thin  tense 
walls.  The  histological  structure  of  the  honey  stomach  (fig.  45,  IIS) 
is  exactly  the  same  as  that  of  the  oesophagus.  The  numerous  high 
folds  into  which  its  epithelium  (Epth)  is  thrown  permit  the  enor- 
mous expansion  of  which  the  sac  is  capable.  When  a  worker  with 
its  honey  stomach  filled  with  nectar  reaches  the  hive,  the  nectar  is 
either  stored  directly  in  a  cell  or  is  given  up  first  to  some  otlier 
worker,  who  places  it  in  a  cell. 

It  would  appear  that  all  the  food  swallowed  by  a  bee  must  go  first 
into  the  honey  stomach,  and  since  the  bee's  diet  consists  of  pollen  and 
honey  as  well  as  nectar,  one  would  suppose  that  in  regurgitating  the 
latter  the  bee  w^ould  also  disgorge  the  pollen  it  might  have  recently 
eaten.  Honey  Avhich  is  made  from  the  regurgitated  nectar  does 
indeed  contain  some  pollen,  but  most  of  the  ])ollen  eaten  by  the  bee 
is  undoubtedly  retained  in  the  stomach  as  food.  The  apparatus  by 
means  of  which  the  pollen  is  supposed  to  be  separated  from  the  nec- 
tar belongs  to  the  following  division  of  the  alimentary  canal,  but  it 
is  not  known  that  the  worker  takes  nectar,  and  pollen  for  food,  into 
its  honey  stomach  at  the  same  time. 

The  proventriculus  (figs.  42  and  44,  Pvent)  forms  the  necklike  stalk 
between  the  honey  stomach  (HjS)  and  the  true  stomach  or  ventricu- 
lus  (Vent),  but  a  very  important  part  of  it  also  projects  up  into  the 
honey  stomach  (fig.  44  C).  If  the  honey  stomach  be  slit  open,  a 
short,  thick,  cylindrical  object  wall  be  seen  invaginated  into  its  jdos- 
terior  end  and  having  an  X-shaped  opening  at  its  summit  (fig.  44  C, 
nn).  This  opening  is  the  mouth  of  the  proventriculus,  and  its  four 
triangular  lips,  which  are  thick  and  strong,  mark  four  longitudinal 
ridges  of  the  proventricular  tube.  This  structure  is  commonly  known 
as  the  "  stomach-mouth  "  and  is  supposed  to  be  an  apparatus  de- 
signed especially  to  enable  the  worker  to  pick  out  pollen  grains  from 
the  honey  stomach  and  swallow^  them  on  down  into  the  true  stomach 
or  ventriculus,  while  the  nectar  is  left  to  be  stored  in  the  hive. 
Cheshire  says :  ''  While  the  little  gatherer  is  flying  from  flower  to 
flower  her  stomach-mouth  is  busy  separating  pollen  from  nectar." 
This  notion  is  so  prevalent  among  bee  writers  in  general  that  it 
passes  for  a  known  truth.  Yet  it  has  really  never  been  shown  that 
the  worker  eats  pollen  while  she  is  gathering  nectar.  Probably  no 
more  pollen  is  ever  mixed  w^ith  the  nectar  in  the  honey  stomach  than 
is  found  in  the  honey  itself.  Furthermore,  under  normal  ccmditions 
pollen  never  accumulates  in  the  honey  stomach,  even  when  the  bee 


96  THE  ANATOMY  OF  THE  HONEY  BEE. 

is  not  collecting  nectar — or,  at  least,  the  writer  has  not  observed  it — 
while,  finally,  both  the  proventriculus  and  its  mouth  are  just  as  well 
developed  in  the  queens  and  drones  as  in  the  workers,  though  neither 
of  the  former  are  known  to  eat  pollen,  and  they  certainly  do  not 
gather  nectar. 

If  the  honey  stomach  be  cut  open  in  a  freshly  killed  bee,  the 
proventricular  mouth  may  be  seen  still  in  action.  The  four  lips 
spasmodically  open  wide  apart  with  a  quivering  motion  and  then 
tightly  roll  together  and  sink  into  the  end  of  the  proventricular 
lumen.  This,  of  course,  suggests  their  picking  pollen  out  of  the 
nectar,  but  it  is  probably  simply  the  ordinary  process  by  means  of 
which  the  proventriculus  passes  any  of  the  food  in  the  honey  stomach 
on  to  the  ventriculus.  Nearly  all  insects  have  some  such  proventricu- 
lar apparatus,  which  simply  takes  the  stored  food  from  the  crop  as 
it  is  needed  by  the  stomach.  In  some  insects  it  forms  apparently  a 
straining  apparatus,  which  prevents  coarse,  indigestible  fragments 
from  entering  the  stomach,  while  in  some  the  proventriculus  may  be 
a  triturating  organ  comparable  with  a  bird's  gizzard.  Bees,  how- 
ever, do  not  crush  the  pollen  either  in  their  mandibles  or  in  the 
proventriculus,  for  it  occurs  in  perfect  condition  in  the  ventriculus. 

Hence,  before  the  current  notion  that  the  "  stomach-mouth  ''  is 
for  the  special  purpose  of  taking  pollen  out  of  the  nectar  in  the 
honey  stomach  can  be  accepted  it  must  be  first  demonstrated  that 
the  workers  eat  pollen  while  the  honey  stomach  contains  nectar  to 
be  stored  in  the  cells,  i.  e.,  any  more  than  is  disgorged  along  with 
the  nectar;  and,  secondly,  a  reason  must  be  shown  wh}^  the  queens 
and  drones  should  have  a  "  stomach-mouth  "  as  well  developed  as 
that  of  the  worker.  In  the  meantime  it  appears  most  logical  to 
regard  the  proventricular  mouth  as  simply  the  ordinary  apparatus, 
possessed  by  insects  in  general,  by  means  of  which  all  of  the  food  is 
passed  from  the  crop  to  the  stomach. 

A  longitudinal  section  through  the  honey  stomach,  the  proventric- 
ulus, and  the  anterior  end  of  the  ventriculus  is  shown  in  figure  45, 
which  is  made  from  a  queen.  The  proventriculus  does  not  differ  from 
that  of  a  worker,  but  the  honey  stomach  is  snuiller  and  not  so  much 
turned  to  one  side  (cf.  fig.  44  A  and  B).  The  two  muscle  hiA^ers  of 
the  (psophagus  continue  down  over  the  walls  of  the  honey  stouiach 
{TM(i  and  LMcl).  The  outer  layer  of  transverse  fibers,  however, 
ceases  at  the  posterior  end  of  this  organ,  while  the  longitudinal  fil)ers 
continue  posteriorly  over  the  proventriculus  and  the  ventriculus  as 
an  external  layer  {LMcl).  A  new  layer  of  internal  transverse  fibers 
begins  ou  the  proventricular  walls  and  extends  backward  on  the 
ventriculus  ( 7'J/r/)  beneath  the  longitudinals.  Hence  the  muscles 
on  the  (esophagus  and  crop  are  in  reverse  order  from  those  of  the 
proventriculus  and   ventriculus.     The   proventriculus   is  deeply   in- 


THE   ALIMENTARY    CANAL   AND    ITS   GLANDS. 


97 


vaginatecl  into  the  posterior  end  of  the  honey  stoinjich.  Each  h)be 
of  its  mouth  forms  a  thick  trianouhir  vid^e  on  the  walls  of  its 
lumen,  in  which  lies  a  special  mass  of  longitudinal  nniscle  fibers 
{LMcl).  The  epithelium  of  the  lumen  is  lined  by  a  thick,  smooth, 
chitinous  intima  (Inf).  while  the  lobes  of  the  month  (////)  are  pro- 
vided with  bristles  point- 
ing inward  and  backward 
into  the  mouth  opening. 

The  posterior  opening 
of  the  proventriculus  into 
the  ventriculus  is  guarded 
by  a  long  tubular  fold 
of  its  epithelium  (fig.  45, 
PventVlv),  the  pro  ventric- 
ular valve.  This  would 
appear  to  constitute  an 
effective  check  against  the 
escape  of  any  food  back 
into  the  proventriculus.  It 
looks  like  one  of  those  traps 
which  induces  an  animal  to 
enter  by  a  tapering  funnel 
but  whose  exit  is  so  small 
that  the  captive  can  not 
find  it  from  the  other  side. 
Yet  Schonfeld  has  elab- 
orately described  experi- 
ments by  means  of  which 
he  induced  the  ventriculus 


LMci 


— Epth 


Vent 


to    discharge    its    contents 


^-LMcJ 


-TMci 


Fig.  45. — Longitudinal  median  section  of  base  of 
oesophagus  ((E), honey  stomach  (iJ/S), proventricu- 
lus (Pvent)  and  ventriculus  (Vent)  of  a  queen. 


through  the  proventriculus 
into  the  honey  stomach  and 
even  into  the  end  of  the 
oesophagus.  He  says  that 
he  did  this  by  gently  tap- 
ping on  the  honey  stomach 
and  the  ventriculus  at  the 
same  time.  The  experiment 
was  repeated  many  times  Avith  unvarying  results  and  Schonfeld  de- 
scribes so  minutely  what  happened  that  we  can  not  disbelieve  his 
statements.  From  these  experiments  he  argues  that  the  larval  food- 
stuff is  prepared  in  the  stomach  and  regurgitated  through  the  proven- 
triculus directly  into  the  oesophagus  by  a  contraction  of  the  honey 
stomach  which  brings  the  stomach-mouth  against  the  base  of  the  oesoph- 
22181— No.  18—10 7 


98     .         THE  AXATOMY  OF  THE  HONEY  BEE. 

agiis.  AVe  shall  have  to  postpone  a  further  discussion  of  this  subject 
to  page  99.  after  the  ventriculus  and  its  contents  have  been  described. 

The  ventriculus  (fig.  42,  Vent)  is  the  largest  part  of  the  alimentary 
canal  in  the  bee  and  is  bent  into  a  U-shaped  loop  of  ^Yhich  the  pos- 
terior arm  is  dorsal.  It  is  cylindrical  and  does  not  vary  so  much  in 
shape  and  diameter  according  to  its  contents  as  do  the  other  parts  of 
the  canal,  although  the  numerous  transverse  constrictions  which  give 
it  a  segmented  appearance  are  not  at  all  constant.  When  examined 
under  alcohol  the  ventriculus  has  an  opaque  whitish  appearance,  but 
hi  the  natural  condition — that  is,  as  seen  when  examined  in  a  freshly 
killed  or  asphyxiated  bee — it  is  of  a  dark -brown  color  with  lighter 
rings  corresponding  to  the  constrictions.  The  latter  represent  in- 
ternal folds  where  the  walls  are  really  thicker  than  elsewiiere,  the 
color  being  due  to  the  contents  which  naturally  show  more  plainly 
through  the  thin  parts. 

The  contents  of  the  ventriculus  invariably  consist  of  a  dark  brown 
mucilaginous  slime  and  generally  also  of  a  varying  amount  of  pollen. 
The  latter  is  most  abundant  in  the  posterior  arm  of  the  ventricular 
loop  and  is  often  densely  packed  in  its  rear  extremity,  while  the  an- 
terior arm  may  be  almost  entirely  free  from  it.  The  pollen  in  the 
ventriculus  is  always  fresh-looking,  the  native  color  showing  dis- 
tinctly through  the  enveloping  slime  while  most  of  the  grains  yet  re- 
tain all  of  their  contents.  The  writer  has  examined  many  samples 
of  pollen  from  the  stomachs  of  workers  and,  in  all,  the  great  mass  of 
it  showed  no  evidence  of  digestion,  the  color  being  fresh  and  the 
contents  j^erfect — only  a  few  had  the  latter  shrunken  and  seldom  was 
an  empty  shell  observed.  On  the  other  hand,  the  pollen  contained 
in  the  small  intestine  has  invariably  lost  its  bright  color,  the  contents 
of  the  majority  of  the  gi-ains  are  more  or  less  shrunken,  while  a  num- 
ber of  empty  shells  are  to  be  found.  That  in  the  rectum,  finally,  con- 
sists in  large  part  of  empty  shells  or  of  grains  having  the  contents 
greatly  shrunken  and  appaix^ntly  mostly  dissolved  out,  although  a 
few  perfect  and  bright-colored  grains  are  always  present,  looking  as 
if  entirely  unatl'ected  by  the  digestive  liquids.  From  these  observa- 
tions the  writer  would  conclude  that  the  digestion  of  pollen  takes 
place  ])rin('ipally  in  the  intestine.  In  all  parts  of  the  alimentary 
tract  there  occur  numerous  bits  of  feathered  bee-hairs,  but  these  seem 
to  be  esi)ecially  numerous  in  the  ventriculus. 

We  are  now  in  a  })()siti()n  to  discuss  the  i)ossibility  of  the  production 
of  the  brood  food  in  the  stomach.  Sch()nfeld  (ISSG),  as  has  already 
been  stated,  argues  that  this  substance  is  regurgitated  "chyle"  from 
the  ventriculus.  Arnhart  (lOOG)  adoi)ts  this  view  and  elaborates 
considei'ably  upon  the  chemical  pi'ocess  by  means  of  which  the  trans- 
foruiation  of  "chyle*'  into  this  larval  food  is  eH'ected  through  the 
addition  of  tartaric  acid   from  the  pharyngeal  glands  of  the  head. 


THE   ALIMENTARY    CANAL   AND   ITS   GLANDS.  99 

The  ventricular  contents  do  become  slightly  milky  when  treated  with 
a  solution  of  tartaric  acid,  but  they  are  not  chan<red  into  anything 
at  all  resembling  royal  jelly.  Moreover,  a  transfoi-mation  of  the 
brown  slimy  contents  of  the  ventriculus  into  the  white  gummy  paste 
on  which  the  larvae  are  fed  does  not  seem  possible  without  the  addi- 
tion of  much  other  material.  In  fact  the  added  matei'ial  must  make 
up  the  conspicuous  part  of  the  larval  foodstuff  and,  from  a  purely 
argumentative  standpoint,  it  would  not  seem  necessary  to  assume  that 
it  contains  any  "  chyle  "  at  all.  Again,  if  it  were  not  for  Schonfeld's 
experiments  one  could  not  easily  believe  that  the  food  could  be  dis- 
gorged through  the  proventricular  valve.  The  conspicuous  action  of 
the  proventricular  mouth  is  a  swallowing  motion,  and  the  writer  has 
not  been  able  to  induce  the  ventriculus  to  disgorge  its  contents 
through  it  in  the  way  that  Schonfeld  describes,  although  perhaps 
sufficient  care  w  as  not  observed  in  exposing  the  organs.  Cheshire 
states  that  the  proventricular  tube  (fig.  45,  PrentVIv)  in  the  ventricu- 
lus '•  rather  makes  regurgitation  improbable  than  impossible."'  while 
he  argues  that  the  down-pointing  bristles  of  the  stomach-mouth  would 
further  interfere  with  this  process.  Cowan  adopts  the  view  of 
Dufour  and  Schonfeld  that  the  brood  food  is  of  ventricular  origin, 
and  says  in  this  connection:  "Although  saliva  from  the  glands 
(especially  System  I)  is  probably  added  to  the  food,  this  can  not, 
from  its  great  variabilitv.  be  entirely  a  secretion,  as  stated  by 
Schiemenz.  The  work  of  Doctor  Planta,  we  think,  conclusively  proves 
that  the  food  is  not  a  secretion,  and  that  the  nurses  have  the  power 
of  altering  its  constituents  as  may  be  required  for  the  different  bees." 
If  the  variation  of  the  food  is  under  the  control  of  the  workers  pro- 
ducing it.  it  does  indeed  look  impossible  that  it  should  be  produced 
entirely  by  glands.  Cowan  illustrates  by  a  diagram  how  regurgita- 
tion through  the  proventriculus  may  be  possible  in  spite  of  the  pro- 
ventricular tube  projecting  into  the  ventriculus.  Since  this  tube  is 
simply  a  cylindrical  fold  its  walls,  as  shown  in  figure  45,  Pi'entVlv^ 
consist  of  tw  o  layers,  and  Cowan  says  that  '*  when  the  bee  wishes  to 
drive  the  chyle  food  from  the  chyle-stomach  {Vent)  into  the  cells 
it  forces  the  stomach-mouth  {nn)  up  to  the  oesophagus  {(E)  and  the 
prolongation  {PventVlv)  unfolds,  extending  the  chyle-stomach  to  the 
oesophagus,  making  a  direct  communication  through  which  the  food 
is  forced  by  compression  of  the  chyle-stomach  by  its  muscles."  The 
honeA'-stomach  of  the  worker  is  much  larger  than  that  of  the  queen, 
shown  by  figure  45.  in  which  there  is  not  enough  space  for  the  unfold- 
ing of  the  proventricular  tube.  This  mechanism  suggested  by  Cowan 
looks  simple  and  conclusive  in  a  diagram,  but  when  one  attempts  to 
unfold  the  proventricular  tube  by  grasping  the  stomach-mouth  in  a 
pair  of  fine  forceps  and  pulling  the  top  of  the  proventriculus  upward 
it  is  found  that,  while  the  tube  can  be  entirely  straightened  out,  doing 


100  THE  ANATOMY  OF  THE  HONEY  BEE. 

SO  involves  the  tearing  of  all  the  fine  muscle  fibers  and  tracheal 
branches  uniting  the  honey-stomach  to  the  upper  end  of  the  ventricu- 
lus  (fig.  4:5).  If,  then,  the  organ  itself  can  not  be  made  to  work 
according  to  this  scheme,  it  might  be  supposed  that  the  inner  wall  of 
the  proventriculus  and  the  tube  are  evaginated  through  the  stomach- 
mouth  (nn),  but  the  walls  of  the  former  certainh^  appear  to  be  en- 
tirely too  rigid  to  permit  of  any  such  performance  as  this.  Finally, 
it  is  not  clear  how  any  eversion  of  the  tube  could  be  produced  by  the 
proventricular  muscles  as  the}^  exist. 

The  various  facts  and  arguments  bearing  on  the  origin  of  the 
brood  food  may  be  summarized  as  follows: 

1.  The  brood  food  itself  is  a  milky- white,  finely  granular,  and 
gummy  paste  having  a  strong  acid  reaction  said  to  be  due  to  the 
presence  of  tartaric  acid. 

2.  The  pharyngeal  glands  of  the  head  are  developed  in  proportion 
to  the  social  specialization  of  the  various  species  of  bees;  they  are 
always  largest  in  those  individuals  that  feed  the  brood,  and  they 
reach  their  highest  development  in  the  workers  of  the  honey  bee. 
From  this  it  would  seem  that  they  are  accessory  to  some  special 
function  of  the  worker. 

3.  The  contents  of  the  stomach  in  the  workers  consist  of  a  dark 
brown,  slimy,  or  mucilaginous  substance  in  no  way  resembling  the 
brood  food,  even  when  acidulated  with  tartaric  acid.  Pollen  is 
present  in  varying  quantity,  mostly  in  the  posterior  end  of  the 
stomach,  and  shows  little  or  no  evidence  of  digestion.  Since  the 
brood  food  is  highly  nutritious,  it  must  contain  an  abundance  of 
nitrogenous  food  material  which  is  derived  only  from  pollen  in  the 
bee's  diet.  Therefore  it  is  not  clear  hoAV  the  stomach  contents  can 
alone  form  brood  food. 

4.  The  constituents  of  the  food  given  to  the  different  larva\  at 
different  stages  in  their  growth,  and  to  the  adult  queens  and  drones 
show  a  constant  variation  apparently  regulated  by  the  workers  pro- 
ducing it.  A  variation  of  this  sort  can  not  be  explained  if  it  is 
assumed  that  the  brood  food  is  produced  by  the  glands  alone. 

5.  Powdered  charcoal  fed  to  a  hive  of  bees  appears  after  a  short 
time  in  the  brood  food  in  the  cells,  and  this  has  been  urged  as  proof 
that  the  latter  is  regurgitated  "  chyle."  But  it  is  certainly  entirely 
possible  that  the  charcoal  found  in  the  food  might  have  come  only 
from  the  honey  stomach  or  even  from  the  (rsophagus  or  mouth. 

0.  We  have  Schonfeld's  word  for  the  statement  that  a  regurgita- 
tion of  the  stomach  contents  may  be  artificially  induced  by  irritation 
of  the  honey  stomach  and  ventricuhis  in  a  freshly  dissected  bee,  but 
all  explanations  ollered  to  show  how  this  is  mechanically  possible 
in  sj^ite  of  the  proventricular  valve  are  unsatisfactory  when  the 
actual  anatomical  structure  is  taken  into  consideration. 


TITK    AI/IVIF.XTARY    CANAT^    AND    ITS    CLANDS.  101 

The  only  coiiclusion,  then,  that  we  arc  really  w  aii-ante<l  in  (haw- 
ing concerning  the  origin  of  the  royal  jelly  or  of  any  of  th(>  larval 
food  paste  is  that  we  do  not  know  anything  about  it.  (Mieshii-e  is 
probably  responsible  for  the  widespread  opinion  that  it  is  formed 
by  the  pharyngeal  glands,  though  Schiemenz  (1883)  published  a 
large  paper  containing  this  theory  three  years  before  Cheshire's 
book  was  printed.  The  "  chyle  ''  theory,  which  also  has  many  advo- 
cates, originated  with  Dufour  but  was  principally  elaborated  by 
Schonfeld.  Arnhart  would  derive  the  brood  food  from  both  the 
stomach  and  the  glands.  But  we  are  still  absolutely  in  the  dark, 
since  we  lack  definite  and  conclusive  information.  A  satisfactory 
study  of  the  subject  would  involve  the  chemical  investigation  of 
very  minute  quantities  of  substances,  and  it  may  be  a  long  time  before 
any  interested  person  is  found  capable  of  undertaking  a  work  of  this 
sort.  The  writer  of  the  present  paper  is  professedly  preparing  an 
account  only  of  the  structure  of  the  organs,  but  is  doing  this  with 
the  hope  that  it  may  furnish  a  basis  for  some  future  investigator  who 
shall  have  time  to  devote  himself  to  a  study  of  the  chemistry  and 
physiology  of  the  digestive  organs  and  their  glands. 

In  vertebrate  animals  the  digestive  secretion  of  the  stomach  is  acid 
and  its  enzymes  bring  about  especially  the  digestion  of  proteids.  The 
resulting  acid  mixture  is  called  chyme.  In  the  intestine  the  contents 
are  flooded  with  various  alkaline  liquids  whose  enzymes  then  take  up 
the  digestion  of  the  other  food  elements.  The  final  prepared  product, 
which  is  absorbed  by  the  lacteals,  is  called  chyle.  These  names  have 
been  applied  to  the  contents  of  the  alimentary  canal  in  insects — espe- 
cially by  Arnhart  (1906),  who  speaks  of  the  material  undergoing 
digestion  as  "  chyme  "  and  the  completed  products  as  "  chyle."  But 
absolutely  nothing  is  known  of  the  digestive  process  in  insects  beyond 
the  fact  established  by  Plateau  (1874)  that  the  contents  of  all  parts  of 
the  alimentary  tract  are  alkaline  during  digestive  activity  and  either 
neutral  or  weakly  alkaline  at  other  times.  Hence,  if  we  make  use  of 
these  words  in  insect  physiology,  it  must  be  with  the  understanding 
that  no  chemical  significance  is  implied.  The  ventriculus  is  very 
commonly  called  the  ''  chyle  stomach  "  but  there  is  probably  no  reason 
for  calling  it  a  ''  chyle  stomach  "  any  more  than  a  "  chyme  stomach,*' 
and  likewise  there  is  no  reason  for  supposing  that  the  intestine  does 
not  contain  chyle — in  fact,  it  almost  certainly  does.  The  w^ord 
"  chyle  ''  may  be  used  with  entire  propriety  in  insect  physiology  to 
signify  the  completed  products  of  digestion,  but  to  designate  a  part 
of  the  alimentary  tract  as  the  "  chyle  stomach  "  is  applying  the  term 
w^ithout  an  adequate  basis  of  facts. 

The  contents  of  the  ventriculus  are  surrounded  by  several  concen- 
tric layers  of  thin  filmy  membrane  w^hich  form  an  interior  tube  ex- 
tending the  entire  length  of  the  stomach  and  reaching  down  into  the 


102  THE  ANATOMY  OF  THE  HONEY  BEE. 

anterior  end  of  the  intestine.  This  tube  can  be  ver}^  easily  seen  by 
carefully  cutting  open  the  outer  walls  of  the  ventriculus,  but  it  is 
best  demonstrated  by  transverse  microtome  sections  of  a  specimen 
jDrepared  for  histological  purposes.  Such  a  section  is  shown  by  figure 
46  A.  A  small  amount  of  solid  food  matter  {qq)  is  seen  in  the  cen- 
ter of  the  specimen,  surrounding  which  are  numerous  irregular  con- 
centric rings  of  membrane  {Pmh)^  some  adhering  to  each  other  in 
places,  others  entirely  free,  most  of  them  structurele.-s.  but  others 
partl}^  cellular.  These  are  known  as  the  peritrophlc  m  mhranes 
{Pmh).  They  keep  the  solid  contents  of  the  stomach  away  from  the 
epithelial  walls,  from  which,  as  will  be  presently  explained,  they  are 
given  off  from  time  to  time. 

The  walls  of  the  ventriculus  (fig.  46  A)  are  thick  and  consist  of 
numerous  cells  (Epth)  apparently  very  irregularly  arranged.  On 
their  inner  surfaces  is  a  thin  intima  (Int)  and  on  their  outer  surfaces 
a  still  finer  basement  membrane  (BM).  Outside  of  the  last  are  two 
layers  of  muscles,  the  external  layer  consisting  of  longitudinal  fibers 
(LMcl)  and  the  inner  of  transverse  ones  (TMcl).  Numerous  an- 
nular depressions  of  the  walls  form  internal  folds  (fig.  45),  but  any 
part  of  the  ventricular  wall  can  be  stretched  out  into  a  flat  sheet, 
which  is  then  seen  to  be  full  of  little  pits,  giving  the  whole  a  screenlike 
appearance.  Sections  show  that  the  pits  result  from  circular  invagi- 
nations of  the  basement  membrane  (fig.  46  B,  BM),  and  that  at  the 
bottom  of  these  pockets  the  cells  are  very  small  and  convergent,  wdiile 
those  on  their  lips  are  very  large.  Figure  46  B  is  a  very  perfect 
example  of  this  structure  of  the  epithelium,  which  is  usually  more 
or  less  obscured,  as  in  figure  46  A,  by  a  great  proliferation  of  small 
cells  from  the  lips  of  the  cups — and  then  a  large  section  seldom  gives 
a  symmetrical  view  of  all  the  parts.  The  cups  are  all  filled  to  over- 
flowing by  a  gelatinous  mass  (pp)  which  fuses  over  their  edges  into 
a  continuous  coating  beneath  the  intima  over  the  entire  inner  surface 
of  the  epithelium.  This  mass  a})pears  to  be  formed  mostly  by  the 
cells  at  the  bottoms  of  the  cups,  for  the  outermost  of  these  (fig.  46  B, 
rr)  often  insensibly  fade  into  it. 

Figure  46  E  shows  an  opjiosite  condition  of  the  epithelial  cells. 
Here  the  lip  cells  of  the  cups  appear  to  be  very  actively  dividing, 
and  proliferating  a  great  number  of  small  cells  {Knz)  which  float 
off  into  the  gelatinous  covcM'ing.  These  discharged  cellules  are  all 
nucleated,  but  their  protoplasui  does  not  stain  in  |)i'eparations  and 
consequently  they  appcnr  clein'  and  (nmsparent  as  couiparcMl  with  the 
cells  they  appareutly  come  froui.  The  writer  has  not  been  able  to  find 
any  of  these  cells  actually  in  the  i)i'()('(»ss  of  division,  but  a  comparison 
of  figures  B  and  K  (which  are  camera  lucida  drawings  ;ind  not  dia- 
gnmis)  would  certaiidy  suggest  that  the  condition  of  the  cells  in  F 
has  resulted  from  a  very  active  division  of  the  cells  of  the  walls  and 


THE    ALTMRNTAHY    ("ANAL   AND    ITS    (JLANDS. 


103 


lips  of  the  cups,  which  are  quiescent  in  B.  Coniparirifr  (|iis  with 
what  is  known  to  take  phice  in  other  insects  durin<^  (li<(estion,  there 
is  every  reason  for  believing  that  the  proliferated  ceHules  are  filled 
with  the  digestive  secretion,  and  that  E  represents  a  stage  immedi- 


LMcl 


Pmb 


Fig.  46. — Histological  details  of  alimentary  canal  of  worker  :  A,  cross  section  of  ventriculus 
showing  peritropliic  membranes  (Pmb)  ;  B,  section  of  wall  of  ventriculus  showing 
epithelial  cups  with  cells  in  resting  condition  and  covered  by  gelatinous  mass  (pp)  ; 
C,  section  of  Malpighian  tubule ;  D,  cross  section  of  small  intestine ;  E,  section  of 
ventricular  epithelium  after  formation  of  numerous  small  digestive  or  enzyme  cells 
(En::)  given  off  into  gelatinous  matrix  (pp)  ;  F,  section  of  anterior  end  of  rectum 
through  rectal  glands  {RGl)  ;  G,  part  of  slightly  oblique  section  through  posterior  end 
of  ventriculus  and  anterior  end  of  small  intestine,  showing  openings  of  Malpighian 
tubules  {Mai)   into  the  latter. 

ately  subsequent  to  one  of  greatest  secretive  activity,  in  which  there 
is  a  large  number  of  little  cells  {Enz)  highly  charged  with  the 
enzyme-containing  digestive  juices  imbedded  in  a  gelatinous  matrix 
covering  the  inner   surface  of  the  epithelium.     This  matrix  next 


104  THE  AXATOMY  OF  THE  HONEY  BEE. 

separates  itself  from  the  ends  of  the  remaining  epithelial  cells,  which 
at  the  same  time  secrete  a  new  intima  over  their  inner  surfaces.  The 
lower  part  of  figure  4G  A  shows  this  indisputably.  The  whole  thing, 
then,  finally  contracts  about  the  food  and,  as  the  digestive  cellules 
give  up  their  contents,  shrivels  and  shrinks  and  becomes  a  peritrophic 
membrane.  In  figure  A  the  outermost  peritrophic  layer  is  still  in 
both  conditions — its  dorsal  part  is  shrunken  to  a  thin  membranous 
form,  while  its  loAver  part  is  gelatinous  and  filled  with  secretion 
cellules,  though  it  is  separated  from  the  epithelium  by  a  new  intima 
and  is  detached  at  intervals  from  the  latter.  Beneath  the  new  intima, 
furthermore,  is  seen  at  places  the  formation  of  a  new  gelatinous  mass. 
Some  of  the  inner  peritrophic  layers  shown  in  A  also  retain  remnants 
of  cells. 

Figure  46  A  is  drawn  from  a  specimen  which  is  typical  of  all  in 
several  series  of  sections  through  the  ventriculus.  The  peritrophic 
laj^er  partly  adhering  to  the  epithelium  is  no  artifact,  because  the 
same  condition  may  often  be  directly  observed  in  dissections  of  fresh 
specimens.  In  the  opposite  end  of  the  series  from  which  the  specimen 
was  selected  this  layer  is  entirely  free  from  the  epithelium. 

The  peritrophic  membrane  has  been  described  in  some  insects  as 
being  a  ^prolongation  from  the  intima  of  the  proventriculus,  the  ven- 
triculus itself  being  supposed  never  to  secrete  an  intima.  It  is  per- 
fectly conceivable  that  the  anterior  end  of  the  membranes  might  be 
generated  by  the  outer  cellular  layer  of  the  proventricular  funnel  and 
remain  attached  to  it  after  the  rest  of  it  had  become  free  from  the 
ventricular  wall,  and  thus  give  the  appearance  of  belonging  to  the 
j^roventriculus.  The  writer,  hoAvever,  has  several  sets  of  longitudinal 
sections  through  these  parts  in  the  bee,  but  none  of  them  nor  any  dis- 
sections made  show  such  a  condition. 

Absorption  is  commonly  supposed  to  take  place  largely  in  the  ven- 
triculus. If  so,  the  food  must  pass  through  the  several  peritrophic 
membranes  and  then  through  the  thick  epithelium.  It  is  entirel}^ 
jDossible  that  it  may  do  so,  but  the  pollen  contained  in  the  ventriculus, 
as  already  stated,  shows  little  or  no  evidence  yet  of  digestion  and  does 
not  ])egin  to  do  so  until  it  reaches  the  small  intestine.  On  the  other 
hand,  the  dark  mucilaginous  slime  of  the  ventriculus  does  not  appear 
in  any  quantity  in  the  much  drier  contents  of  the  small  intestine. 
Therefore  it  may  be  sui)p()sed  that  this  slime  contains  the  sugar  ele- 
ments of  tlie  food  and  that  the  latter  are  principally  digested  in,  and 
absorbed  from,  the  ventriculus.  The  absorption  of  the  proteids  and 
hydrocarbons  nnist  take  place  in  the  iutestine  and  rectum  since  these 
food  elements  in  the  bee's  diet  are  derived  only  from  the  pollen. 
However,  these  conclusions  are  ])urely  tentative,  being  based  on  the 
writer's  observation  of  the  contents  of  the  different  parts  of  the  ali- 
mentary tract,  which,  while  fairly  extensive  and  continued  through 


THE   ALIMENTARY   CANAL   AND    ITS    (; LANDS.  105 

most  of  a  year,  are  confessedly  not  nearly  a(le(iuale  to  serve  as  a 
basis  for  conclusive  statements  on  the  (li<^estive  process.  They  are 
sufficient,  however,  to  show  the  utter  lack  of  a  basis  in  facts  for  many 
other  opinions  on  this  subject. 

Cheshire  (1886)  describes  two  kinds  of  cells  in  the  ventricular 
epithelium,  ''one  secreting  a  digestive  fluid  (gastric  juice)  from  the 
surrounding  blood  into  the  stomach,  so  that  the  pollen  grains  may  he 
made  fit  for  assimilation  by  a  transformation  not  unlike  that  lique- 
fying gluten  in  our  own  case;  the  other  absorbing  the  nutrition  as 
prepared  and  giving  it  up  to  the  blood."  Though  Cheshire  refers 
to  his  figures  to  show  these  two  kinds  of  cells,  he  docs  not  point  out 
which  are  which — in  fact,  he  does  not  even  designate  two  different 
kinds  in  his  drawings  nor  even  represent  two  kinds. 

The  small  intestine  (fig.  42,  SInf)  forms  a  loop  upon  itself  and  con- 
stitutes a  narrow  tube  connecting  the  stomach  (Vent)  with  the  large 
intestine  or  rectum  (Red).  Its  anterior  end  is  somewhat  enlarged 
and  carries  the  circle  of  malpighian  tubules  (Mai).  Its  epithelium 
(fig.  46  D,  Epth)  is  very  simple  and  is  thrown  into  six  longitudinal 
folds  that  project  into  its  lumen.  On  the  outside  is  a  thick  sheath 
of  transverse  muscle  fibers  (TMcl)  with  distinct  nuclei  (Nn).  The 
latter  are  designated  by  Cheshire  (1886)  as  ''longitudinal  muscles" 
(see  his  figure  14  D),  but  this  is  a  very  evident  mistake — the  small 
intestine  has  no  longitudinal  muscles  at  all.  It  is  evident  that  the 
folds  of  the  epithelium  permit  the  ordinarily  narrow  tube  to  expand 
very  considerably  when  necessary  to  allow  the  passage  of  a  large 
amount  of  food.  The  contents  of  the  small  intestine  are  usually 
drier  than  those  of  the  ventriculus,  consisting  principally  of  masses 
of  partly  digested  pollen,  that  is  to  say,  the  contents  of  the  grains  are 
partly  dissolved  out — presumably  signifying  that  they  are  under- 
going digestion.  There  is  usually  only  a  small  amount  of  the  brown 
slime  present  such  as  fills  the  ventriculus. 

The  Malpighian  tubules  (fig.  42,  Mai)  are  wrapped  and  coiled  about 
one  another  and  about  the  viscera  of  the  abdominal  cavity.  There 
are  about  100  of  them  in  the  honey  bee  and  they  all  open  separately 
into  the  anterior  end  of  the  intestine.  Each  is  a  very  long  thread- 
like tube  consisting  of  a  single  layer  of  epithelial  cells  provided  with 
a  very  delicate  basement  membrane  and  intima  (fig.  46  C).  The  ends 
of  many  of  the  cells  are  clear  and  bulge  into  the  lumen.  Figure 
46  G  shows  a  section  through  the  junction  of  the  ventriculus  and  the 
intestine  where  the  tubules  open  by  narrow  necks  penetrating  the 
epithelium.  The  wall  of  the  ventriculus  forms  a  short  double-layered 
fold  (VentVlv)  projecting  backward  into  the  anterior  end  of  the 
intestine,  behind  which  are  the  orifices  of  the  Malpighian  tubules. 
The  section  from  which  figure  G  was  drawn  is  cut  somewhat  obliquely 
and  takes  in  this  fold  only  on  one  side. 


106  THE  ANATOMY  OF  THE  HONEY  BEE. 

The  Malpigliiaii  tubules  are  regarded  as  excretory  in  function  and 
are  supposed  to  remove  from  the  blood  the  nitrogenous  Avaste  prod- 
ucts resulting  from  metabolism.  Minute  crystals  of  urates  are  often 
to  be  found  in  them  and  they  probably  perform  the  work  of  the 
kidneys  in  vertebrate  animals. 

The  large  intestine  (fig.  42,  Rect)^  called  the  rectum  in  insects,  is 
an  enormous  sac  which  may  lie  limp  and  flabby  in  the  rear  part 
of  the  body  or  it  may  be  so  immensely  distended  by  the  amount  of 
its  solid  and  liquid  contents  as  to  occupy  a  large  part  of  the  abdomi- 
nal cavity.  The  recognizable  elements  of  the  material  within  it 
consist  mostly  of  the  empty  shells  of  pollen  grains  or  of  grains  hav- 
ing their  contents  greatly  shrunken  and  distorted — presumably  as 
a  result  of  the  absorption  of  the  protoplasm,  although  a  considerable 
number  are  usually  present  which  are  only  slightly  digested,  while 
there  are  always  to  be  observed  a  few  perfect  and  fresh-looking 
grains  showing  no  evidence  at  all  of  digestion.  The  rest  of  the  in- 
definite mass  of  solid  rectal  material  consists  of  some  unrecognizable, 
finely  triturated  substance,  probably  derived  in  part  from  fragments 
of  the  peritrophic  membranes.  There  are  always  present  a  few  bits 
of  feathered  bee  hairs. 

The  epithelium  of  the  rectum  is,  like  that  of  the  oesophagus,  rudi- 
mentary, being  distinguishable  only  by  the  nuclei  (fig.  46  F,  Nu) 
remaining  in  the  outer  layer  of  the  thick  transparent  intima  (Int). 
Outside  of  this  is  an  external  layer  of  longitudinal  muscle  fibers 
(LMcI)  and  an  inner  layer  of  transverse  fibers  {TMcl).  The  intima 
{Int)  is  thrown  into  numerous  folds  whose  edges  converge,  forming 
pocketlike  grooves  between  them  in  which  are  lodged  small  masses 
of  the  rectal  contents.  This  is  very  suggestive  that  absorption  takes 
place  in  this  part  of  the  alimentary  tract,  although  it  is  not  com- 
monly supposed  to  do  so,  but  if  the  pollen  is  not  fully  digested  until 
it  reaches  the  rectum,  how  can  it  be  absorbed  by  the  anterior  part 
of  the  alimentary  canal? 

The  so-called  rectal  glands  (fig.  42,  RGl)  consist  of  six  hollow 
epithelial  tubes  (fig.  46  F,  RGl)  and  are  the  only  parts  of  the  rectal 
epithelium  in  which  the  cells  are  well  develoi)ed.  The  cells  on  the 
outside  of  each  "gland"  are  small,  but  the  inner  ones  are  very  large 
and  are  covered  by  a  thick  layer  of  dark  chitin  {Int).  The  lumen 
is  intercellular  and  does  not  communicate  with  that  of  the  rectum. 
When  the  rectum  is  distended  the  "glands"  bulge  out  on  the  surface 
as  six  short  opaque  ridges  (fig.  42,  RGl),  but  when  it  is  empty  they 
sink  into  the  walls  as  in  figure  46  F.  Nothing  is  known  of  the 
function  of  these  organs,  and  their  glandular  nature  is  entirely  con- 
jectural. If  they  are  glands,  it  is  not  clear  why  the  intima  should 
be  so  especially  dense  on  their  inner  faces. 


THE    CIRCULATORY   SYSTEM.  107 

VII.    THE  CIRCULATORY  SYSTEM. 

The  liquid  nKMliuiu  that  distrihiitcs  the  dioc^tcd  food  from  the, 
alimentary  canal  to  Hie  cells  of  the  hody  tissues  is  called  the  Jdood^ 
and  the  contractile  ()r<>an  that  keeps  the  blood  in  motion  is  the  heart. 
In  vertebrate  animals  the  blood  is  contained  entirely  within  tubes 
called  arteries  and  veins,  but  in  insects  and  most  other  invertebrate 
animals  the  blood  simply  fills  the  empty  sj^aces  between  the  viscera 
of  the  body-cavity,  which  spaces  may,  however,  constitute  definite 
channels  or  sinyses^  and  may  even  be  shut  in  by  special  membranes. 
Besides  carrying  and  distributing  the  digested  food  that  is  absorbed 
into  it  in  solution,  the  blood  of  animals  generally  has  also  to  dis- 
tribute oxygen  to  the  tissue  cells  and  carry  off  their  waste  products. 
Oxygen  is  obtained  from  the  air  and,  like  any  other  gas,  is  soluble 
in  liquids.  Hence  it  is  present  in  the  blood  not  in  the  form  of  small 
bubbles  of  gas  but  in  solution,  just  as  it  is  in  all  water  exposed  to  the 
air.  The  respirator}^  system  (see  page  116)  is  simply  a  special  con- 
trivance for  bringing  air  into  close  proximity  to  the  blood  so  that 
its  gases  may  diffuse  into  the  latter,  but  many  soft-bodied  animals 
like  earthworms  absorb  air  directly  through  the  skin.  Vertebrate 
animals  have  a  substance  in  their,  blood  called  hemoglobin  which  is 
contained  in  the  red  corpuscles  and  has  a  great  capacity  for  absorb- 
ing oxygen.  It,  therefore,  enables  the  blood  to  carry  much  more  of 
this  gas  than  could  be  dissolved  simply  in  its  plasma.  Invertebrate 
animals  do  not  need  so  much  oxygen  as  vertebrates,  and,  therefore, 
most  of  them  can  get  along  with  that  which  dissolves  in  the  color- 
less blood  plasma  without  the  special  aid  of  hemoglobin.  Most 
insects,  however,  being  excessively  active  creatures,  must  have  a 
rapid  metabolism  in  their  cell  tissues,  and  consequently  they  need 
much  oxygen  to  consume  the  product  of  this  metabolism,  but  they 
belong  to  the  class  of  animals  without  red  blood  and,  hence,  nature 
has  provided  them  with  another  means  of  obtaining  a  special  supply 
of  air,  namely,  a  set  of  air-tubes  branching  minutely  over  nearly  all 
the  internal  organs,  the  tissues,  and  even  most  of  the  cells  in  the 
body.  (See  "The  Respiratory  System,"  page  112,  for  discussion  of 
oxidation  and  removal  of  waste  products.) 

The  blood  of  insects  is  usually  a  colorless  liquid  containing  opaque 
granular  cells  or  corpuscles  floating  in  it.  There  are  no  special  blood 
vessels,  but  there  are  very  definite  channels  between  the  muscles  and 
viscera  through  wdiich  the  blood  flows,  while  conspicuous  membranes 
stretched  across  the  dorsal  and  ventral  walls  of  the  abdomen  (fig.  1, 
DDph  and  VDph)  inclose  special  dorsal  and  ventral  sinuses  which 
play  an  important  part  in  the  circulation.  These  membranes,  called 
diaphragms^  are  rhythmically  contractile,  and  contribute  much  to 


108 


THE    ANATOMY    OF    THE    HONEY   BEE. 


iiiaintaining  the  circulation  of  the  blood.  The  heart  (fig.  1,  Ht)  is 
located  in  the  dorsal  sinus,  which  latter  is  therefore  often  called  the 
pericardial  chamher.  The  pulsations  of  the  diaphragms  are  produced 
by  fine  muscle  fibers  lying  in  their  walls.  These  are  usually  ar- 
ranged in  a  number  of  fan-shaped  bunches  on  each  side  radiating 
from  the  edges  of  the  diaphragm  (fig.  47,  DpJiMcl)  toward  the  mid- 
dle, where  most  of  them  are  continuous  with  the  fibers  from  the  oppo- 
site side.  It  used  to  be  supposed  that  those  of  the  dorsal  diaphragm 
produced  the  expansion  of  the  heart,  and  they  were  for  this  reason 
called  the  "  wing  muscles  of  the  heart,"  but  the  latter  organ  is  now 
known  to  be  a  muscular  tube  and  to  contract  and  expand  by  its  own 


M.C--5- 


Fig.  47. — Dorsal  diaphragm  of  drone,  from  one  segment  and  adioinine:  parts  of  two 
neighboring  segments,  showing  median  heart  (///)  as  seen  through  transparent  dia- 
phragm {DDijli),  fan-shaped  bunches  of  diaphragm  muscles  (/)/>// .Ur/ 1 .  and  lateral 
tracheal  sac  (TralSc)  giving  off  sac-bearing  trunks  into  pericardial  chamber  above 
diaphragm. 

power.  In  some  insects  the  muscles  of  the  dorsal  diaphragm  form  a 
meshwork  of  fine  fibers  siirroniuliiig  nunierous  hirge  and  small  holes 
in  the  membrane,  which  probably  permit  the  entrance  of  blood  into 
th(^  sinus  above,  but  in  most  species  the  diaphragm  is  imperforate 
and  the  blood  enters  the  pericardial  chamber  above  its  scalloped  edges 
(figs.  1  and  47). 

The  heart  of  insects  in  general  is  a  long  narrow  tube  {i\g;.  1,  Ht) 
situated  in  the  dorsal  sinus  or  pericardial  chamber  of  the  abdomen 
along  the  midline  of  the  body.  It  is  swollen  toward  the  middle  of 
eacth  segment  into  a  /i('<//-f  chamher  {ht)  which  presents  a  vertical 
slit  like   opening  or  ost'iNno    (Ost)    on    each    side.     Theoretically^    in 


THE    CIKCULATOKV    SYSTEM.  109 

generalized  insects,  there  should  \)v  a  clKiinhci-  to  (nicli  s(»gnient,  but 
the  heart  is  variously  shortened  fi-om  hoth  ends  so  that  the  dianibers 
are  always  fewer  than  the  segments.  The  posterior  end  of  the  heart 
is  closed,  but  its  antci-ior  end  ii  i;roduce(l  into  a  long  nari-ow  tube 
called  the  aorta  (fig.  1,  Ao)  which  extends  (liroiigh  Ihc  thorax  and 
opens  by  a  few  simple  branches  into  the  cavity  of  the  head. 

The  heart  of  the  bee  (iig.  1,  /It)  consists  of  only  four  chainbers 
{lht-4ht)  lying  in  the  third,  fourth,  fifth,  and  sixth  segments  of  the 
abdomen.  In  the  front  of  this  part  of  the  body  it  bends  downward 
and  forms  a  large  convoluted  loop  (/)  of  about  1<S  folds  where  it 
passes  through  the  abdominal  constriction.  All  of  this  convoluted 
part  really  belongs  to  the  abdomen,  since  it  lies  in  the  propodeal  part 
of  the  apparent  thorax,  which  is  the  true  first  abdominal  segment. 
The  aorta  (Ao)  extends  forward  from  here  as  a  very  fine  tube  making 
a  large  arch  between  the  muscles  of  the  thorax  and  then  enters  the 
back  of  the  head.  According  to  Pissarew  (1898)  the  convolutions 
of  the  anterior  end  of  the  heart  are  peculiar  to  the  honey  bee,  being 
absent  in  its  nearest  relatives  such  as  Bomhus  and  Megachile.  The 
heart  walls,  as  before  stated,  are  muscular  and  produce  a  rhythmical 
contraction  of  the  tube  whose  pulsations  follow  each  other  from  be- 
hind forward.  Thus  the  contained  blood  is  driven  out  of  the  anterior 
end  of  the  aorta  into  the  head,  where  it  bathes  the  brain  and  the  other 
organs  of  this  region,  and  then  flows  backward,  percolating  through 
the  spaces  between  the  organs  of  the  thorax. 

From  the  thorax  it  enters  the  cavity  of  the  ventral  sinus — not  the 
general  abdominal  cavity,  at  least  in  the  bee — and  is  pumped  back- 
ward by  the  pulsations  of  the  ventral  diaphragm  and  dorsally  over 
the  inner  walls  of  the  thorax  and  through  definite  channels  about  all 
the  viscera,  finally  collecting  in  the  dorsal  sinus  where  it  again  enters 
the  heart  through  the  lateral  ostia.  The  lips  of  the  ostia  are  pro- 
vided with  small  membranous  lobes  which  project  inward  and  con- 
stitute valves  that  prevent  the  expulsion  of  the  blood.  A  similar 
valve  is  placed  at  the  anterior  end  of  each  chamber  of  the  heart  to 
prevent  a  possible  backward  flow. 

In  the  bee,  both  the  dorsal  and  the  ventral  diaphragms  are  well 
developed,  the  former  (fig.  1,  DDph)  extending  from  the  third 
abdominal  segment  to  the  seventh,  inclusive,  while  the  latter  (YDph) 
extends  from  the  abdominal  constriction  to  the  eighth  segment. 
The  ventral  diaphragm  is  much  more  muscular  than  the  dorsal  and 
its  pulsations,  which  are  very  strong,  follow  each  other  from  before 
backward.  They  may  easily  be  observed  by  removing  the  top  of 
the  abdomen  from  an  asphyxiated  bee.  The  ventral  sinus  is  very 
ample,  inclosing  the  nerve  cord  of  the  abdomen,  and  receives  into 
its  anterior  end  the  blood  channels  of  the  thorax,  so  that  the  latter 


110 


THE    ANATOMY    OF    THE    HONEY   BEE. 


comniiinicate  with  the  general  cavity  of  the  abdomen  only  through 
the  ventral  sinus. 

The  dorsal  diaphragm  (fig.  1,  DDph)  ends  by  a  free  transverse 
edge  near  the  front  of  the  third  abdominal  segment.  A  part  of  it  is 
shown  by  figure  47  extending  across  one  segment  and  the  adjoining 
parts  of  two  others.  The  fan-shaped  bunches  of  muscle  fibers 
{DphMd)  are  seen  radiating  from  the  anterior  edges  of  the  terga 
toAvard  the  midline,  where  they  are  mostly  continuous  with  those 
from  the  opposite  side,  only  a  few  of  the  anterior  and  posterior  ones 
ending  free  in  the  membrane  of  the  diaphragm.  The  latter  is  imper- 
forate, but  its  edges  are  deeply  scalloped  between  the  points  where 
the  muscles  are  attached,  allowing  free  entrance  to  the  blood  from 
the  intervisceral  channels  of  the  abdomen.  The  dorsal  surface  of 
the  diaphragm  is  covered  by  a  netAvork  of  cells  (figs.  47  and  48, 
DphCls)  arranged  in  flat  branching  and  fusing  bands.     These  cells 


PphM< 


Fig.  48. — Small  part  of  dorsal  diaphragm  of  drone,  showing  bands  of  flat  diaphragm  cells 
(DphCls),  the  diaphragm  membrane  itself  (Dphmb),  and  the  muscle  fibers  (DphMcl). 

may  be  called  the  diaphrdym  cells  to  distinguish  them   from  the 
pericardial  cells  to  be  described  later. 

The  abdominal  circulation  is  very  easy  to  observe  in  a  living 
bee.  The  best  way  to  demonstrate  it  is  to  pin  an  asphyxiated  bee 
to  a  block  of  cork  or  paraffin  and  remove  the  top  of  the  abdomen 
l)y  making  an  incision  Avith  a  small  pair  of  scissors  clear  around  it. 
(lently  pull  the  alimentary  canal  to  one  side  so  as  to  expose  the 
ventral  diaphragm,  Avhich  Avill  be  observed  pulsating  strongly  back- 
ward. Next  cut  a  small  hole  in  the  top  of  the  thorax  and  insert 
into  it  a  drop  of  some  stain  in  a  Avater  solution  (the  Avriter  used 
carmalum).  Almost  immediately  this  will  appear  in  the  ventral 
sinus  of  the  alxlouuMi.  in  which  it  is  pnm])ed  backward  by  the  dia- 
phragm, and  iVoin  which  it  goes  ui)\vard  through  invisible  channels 
between   the  air  sacs  and   the  alimentary  canal  and  especially  up 


THE    (^KCULATOHY    SYSTEM. 


Ill 


wide  channels  against  the  hiteral  walls  of  eacth  se<j:inen(.  It  does  not 
run  out  free  into  the  abdominal  cavity,  however,  uidess  through  a 
rent,  nor  does  it  enter  the  Litter  fi'oni  the  thorax  except  by  way  of 
the  ventral  sinus.  The  dorsal  circulation  of  course  can  not  be 
observed  in  this  specimen  because  the  back  is  i-emoved.  Therefore, 
take  another  bee  and  fasten  it  in  the  same  mannei',  but  make  simply 
a  shallow  median  slit  along  the  back,  thus  exposing  the  dorsal  sinus 
and  the  heart  from  above.  Now  insert  a  drop  of  stain  into  the 
thorax  as  before.  After  about  two  minutes  this  will  appear  in  per- 
ceptible amount  in  the  dorsal  sinus,  very  much  diluted,  to  be  sure, 
with  the  blood,  but  there  Avill  be  enough  to  give  Avhite  blotting  paper 
a  distinct  red  tint.  In  a  short  time  the  heart  becomes  filled  with 
the  stained  blood  and  appears  as  a  red  tube  along  the  median  line. 

The  dorsal  sinus  contains  not  only  the  heart  but  also  two  pairs  of 
pericardial  air  sacs  in  each  segment.     These  are  seen  entering  the 


Fig.  49. — Pericardial  chamber  of  one  segment  in  worker,  seen  from  below  looking  through 
transparent  dorsal  diaphragm  (DDph),  showing  median  heart  (Ht).  lateral  pericardial 
air  sacs  (HtTraSc)  given  off  from  large  lateral  sacs  (TraSc),  and  the  padding  of 
pericardial  cells  (HtCls)   against  inner  surface  of  tergum   (T). 

sinus  from  the  large  lateral  air  sacs  of  the  abdomen  (TraSc)  in 
figure  1  and  also  in  figure  47.  In  the  latter  the  heart  (Ht)  is  seen 
along  the  median  line  as  it  shows  through  the  diaphragm.  Figure 
49  gives  a  view  of  the  pericardial  sinus  as  seen  from  below,  in  one 
segment,  by  focusing  through  the  transparent  diaphragm  (DDph). 
In  the  middle  lies  a  chamber  of  the  heart  (Ht)  with  the  slitlike 
ostium  on  each  side.  Laterally  are  the  four  pericardial  air  sacs 
(HtTraSc)  giving  off  branches  that  ramify  profusely  upon  the 
heart.  Above  the  heart  and  the  air  sacs  is  a  thick  bed  of  large 
granular  cells  (HtCls)  which  make  a  soft  padding  between  the  hard 
tergal  wall  and  the  delicate  organs  of  the  sinus.  These  are  called 
the  pericardial  cells.  They  may  have  some  physiological  function, 
as  has  often  been  supposed,  but  if  so  no  one  has  decided  what  it  is. 


112  THE    ANATOMY    OF    THE    HONEY    BEE. 

VIII.    THE   RESPIRATORY   SYSTEM. 

The  lives  of  all  animals  depend  upon  a  constant  distribution  of 
free  oxygen  gas  throughout  their  bodies.  This  oxygen,  continually 
inhaled  and  exhaled,  is  not  used  in  the  formation  of  tissues,  it  does 
not  become  a  part  of  the  living  protoplasm  of  the  animal — it  is  the 
physiological  scavenger  that  eats  up  certain  waste  products  of  me- 
tabolism which  are  deadl}'  to  the  system  unless  constantly  removed  or 
changed  into  less  harmful  compounds.  The  action  of  oxygen  upon 
these  waste  substances  within  the  body  is  comparable  with  ordinary 
combustion  in  that  it  results  in  the  formation  of  carbon  dioxid  gas 
and  water  and  in  the  generation  of  heat.  Since  the  air,  which  is  com- 
posed of  both  oxygen  and  nitrogen,  is  the  source  of  the  oxygen  supply, 
the  ordinary  breathing  processes  involve  an  inhalation  also  of  nitro- 
gen gas,  and  the  tissues  become  permeated  with  it  as  Avell  as  with 
oxygen.  The  nitrogen  of  the  air,  however,  is  not  known  to  serve  any 
physiological  purpose  in  the  body,  its  presence  being  simply  unavoid- 
ably incidental  to  the  inhalation  of  oxygen.  AVhile  oxygen  and  nitro- 
gen are  two  most  important  food  elements,  the  tissues  of  animals  can 
not  make  use  of  either  in  the  gaseous  condition,  but  must  be  supplied 
with  substances  containing  these  elements  in  combination  with  others 
in  the  form  of  solid  and  liquid  food  stulfs  taken  into  the  alimentary 
canal.  Hence,  air  is  not  a  food,  and  the  respiratory  system  is  to  be 
regarded  as  chiefly  excretory  in  function. 

The  means  by  which  different  animals  receive  oxygen  into 
their  systems  are  various.  All  aquatic  breathers  of  course  use 
that  which  is  naturally  dissolved  in  water.  Many  of  the  lower  ani- 
mals absorb  air  directly  through  their  skins  and  into  their  tissues, 
while  the  carbon  dioxid  escapes  the  same  Avay.  Others  that  live  in 
the  water  and  whose  bodies  are  covered  by  an  impervious  skin  or 
shell  have  thin-walled,  hollow,  branching  appendages,  called  gills^ 
through  which  the  blood  circulates  freely  and  through  whose  walls 
the  necessary  exchange  of  gases  takes  place.  Land  animals  very 
commonly  have  some  sort  of  an  invagination  from  the  exterior  which 
allows  the  air  to  enter  thin-walled  tubes  or  cavities  and  be  absorbed 
into  the  l)l()()d.  Land  vertebrates  have  a  tube  opening  from  the  back 
of  the  month  wliose  inner  end  branches  j)rofusely  and  forms  a  pair  of 
organs  called  the  lungs,  through  which  the  blood  circulates  freely  in 
delicate  tubes  that  allow  the  transfer  of  gases.  Insects,  finally,  have 
a  system  of  internal  air  tubes,  called  frarhe^v,  opening  to  the  exterior 
by  a  number  of  small  orifices,  called  spit'dclri^,  situated  along  the  sides 
of  the  thoiax  and  abdomen,  which  give  oil'  branches  that  ramify 
minutely  to  ;ill  i)arts  of  the  organism,  thus  virtually  making  a  lung 
of  Ihe  entire  body.    The  trachete  are  thin  tubes  made  of  flat  e2)ithelial 


THE  RESPIRATORY  SYSTEM. 


113 


TraSc 


HtTraSc 


Fig.  50.— Tracheal  system  of  worker  as  seen  from  above,  one  anterior  pair  of  abdominal 
sacs  (fig.  1,  9)  removed  and  transverse  ventral  commissures  of  abdomen  not  shown. 

22181— No.  18—10 8 


I 


114  THE    ANATOMY   OF    THE    HONEY   BEE. 

cells  lined  with  a  delicate  layer  of  chitin.  The  latter,  however,  is 
strengthened  by  circular  thickenings  which  give  the  appearance  of 
an  internal  spiral  thread,  but  a  closer  examination  shows  that  each 
thickening  makes  only  a  few  turns  and  that  several  lie  in  parallel 
bands.  This  structure  is  for  the  purpose  of  maintaining  an  open 
passageway  for  the  air  through  the  ver}^  thin-walled  tubes.  The 
trachea^  branch  into  fine  capillaries  and  these  terminate  in  excessively 
delicate  end-tubes.  In  some  cases  it  is  easy  to  see  that  a  g-reat 
number  of  capillary  branches  surround  the  cells  of  a  tissue,  if 
they  do  not  actually  enter  the  cell  walls,  but  in  others  it  can  not  be 
shown  that  the  tracheae  really  penetrate  below  the  surface  of  a  mass 
of  cells. 

Gases  in  solution,  like  solids,  pass  freel}^  back  and  forth  through 
moist  animal  membranes,  going  in  the  direction  of  the  least  pressure 
of  each  particular  gas.  By  this  simple  method  the  gases  go  back  and 
forth  through  the  walls  of  the  gills,  lungs,  or  air  tubes  and  permeate 
the  tissues  themselves.  Vertebrate  animals,  as  already  explained, 
have  a  red  substance  in  the  blood  called  hemoglobin  which  has  a 
very  great  oxygen-absorbing  power  and  which  greatly  increases  the 
oxygen-carrying  power  of  the  blood,  but  still  a  certain  amount  of 
oxygen  is  carried  in  solution  by  the  liquid  or  plasma  of  the  blood. 
Now,  the  blood  of  insects  has  none  of  this  hemoglobin  and  all  the 
oxygen  it  can  carry  is  that  which  dissolves  in  its  plasma,  but,  on 
account  of  the  extensive  ramification  of  the  air  tubes,  it  is  not  neces- 
sary for  the  blood  to  distribute  the  oxygen  to  the  organs.  It  is  usually 
stated  that  the  bkxxl  in  insects  does  not  carry  oxygen  at  all,  except 
for  its  own  use,  but  it  would  seem  physically  impossible  that  the  gases 
should  not  diffuse  out  of  the  fine  terminal  air-tubes  into  the  blood 
when  they  do  so  in  all  other  cases.  If  the  blood  of  a  crab  or  crayfish 
is  capable  of  carrying  enough  oxygen  in  solution  to  supi)ly  the  wants 
of  the  body,  there  is  no  reason  why  that  of  an  insect,  which  has  much 
better  facilities  for  obtaining  air,  should  not  do  the  same.  Further- 
more, we  can  not  suppose  that  the  products  of  katabolism  have  to 
jicciunulate  about  the  end  trachetc  in  order  to  be  oxidi/AMl.  They  are 
produced  wherever  metabolism  is  going  on,  which  is  everywhere  in 
the  living  cell  substance,  and,  hence,  the  latter  uuist  be  ])ermeate(l 
with  oxygen  in  solution,  which  nuist  also  be  in  the  blood  along  with 
the  carbon  dioxid  formed.  The  carbon  dioxid  difl'uses  back  into  the 
end  tracheae  from  the  blood.  Therefore,  while  the  great  extent  of  the 
tracheal  system  in  insects  relieves  the  blood  of  the  work  of  distribut- 
ing the  oxygen,  the  blood  nuist  nevertheless  serve  as  an  intermediary 
medium  for  both  the  oxygen  and  the  carbon  dioxid  between  the  fine 
terminal  tracheal  branches  and  the  cells. 

It  has  sometimes  been  suggested  that  certain  large  cells  called 
wnocytes^  found  especially  in  connection  with  the  tracheal  system, 


THE  RESPIRATORY  SYSTEM.  115 

function  as  intermediaries  between  the  trachea'  and  tiie  cells,  but 
Koschevnikov  (1900)  has  shown  that  these  cells  appear  to  be  tem- 
porary storehouses  for  waste  products  from  the  tissues — presumably 
uric  acid  comjiounds  which  have  been  already  oxidized.  Even  the 
fat-body  has  been  regarded  as  a  sort  of  limg  in  which  oxidation  takes 
place,  but  there  is  no  evidence  to  support  this  theory,  although,  for 
that  matter,  there  is  little  evidence  in  favor  of  any  theory  in  insect 
phymology. 

The  process  of  metabolism,  or  the  vital  activity  of  the  cells  them- 
selves, results  in  a  breaking  down  of  the  complex  and  highly  unstable 
protoplasmic  molecules  into  chemical  substances  of  much  simpler  con- 
struction, and  it  is  these  by-products  of  metabolism  that  are  attacked 
by  the  oxygen  in  the  blood  furnished  by  the  respiratory  system.  Pro- 
toplasm consists  principally  of  the  elements  carbon,  oxygen,  hydro- 
gen, and  nitrogen,  and  the  oxidation  process  results,  as  before  stated, 
in  the  formation  of  carbon  dioxid  (CO.J  and  water  (H/)),  while 
the  residuary  products  are  mostly  organic  compounds  of  nitrogen 
related  to  uric  acid  (C5H4N4O.O  and  urea  (CON2H2).  The  carbon 
dioxid  is  a  soluble  gas  which  diffuses  into  the  end  tubes  of  the  trachea3 
and  is  exhaled.  A  part  of  the  water  at  least  is  given  off  w^ith  the 
"  breath  "  in  the  form  of  water  vapor,  for  drops  of  it  can  be  collected 
by  inclosing  bees  or  any  insects  in  a  tube  for  a  short  time.  The  nitro- 
gen compounds  and  probably  a  part  of  the  water  are  dissolved  in  the 
blood  and  removed  by  the  Malpighian  tubules,  which  are  the  kidneys 
of  insects. 

Besides  this  oxidation  of  waste  products,  which  allows  the  process 
of  metabolism  to  go  on  unhindered,  the  inhaled  oxygen  serves  also 
another  purpose,  namely,  that  of  maintaining  the  body  heat.  Al- 
though insects  are  usually  classed  as  "  cold-blooded  "  animals,  they 
nevertheless  maintain  a  temperature  which  is  always  higher  than 
that  of  the  surrounding  air  and  is  often  a  number  of  degrees  above 
it.  It  is  Avell  known  that  the  temperature  of  a  beehive  during  the 
brood-rearing  season  is  almost  as  high  as  that  of  the  human  body, 
and  that  even  during  winter  it  remains  at  nearly  80°  F. ;  but  this  is, 
of  course,  due  to  the  accumulation  and  condensation  of  the  warmth 
from  the  bodies  of  a  great  many  bees,  and  is  much  higher  than  the 
temperature  of  any  bee  outside  of  the  hive.  In  our  own  bodies 
certain  substances  are  consumed  by  oxidation  in  the  blood  simply 
to  produce  the  necessary  heat  energy  for  maintaining  metabolism, 
and  hence  it  seems  reasonable  to  suppose  that  the  same  thing  takes 
place  in  insects,  although  of  course  to  a  much  less  degree. 

There  are  generally  ten  pairs  of  spiracles  or  breathing  apertures 
in  insects,  tw^o  being  situated  on  the  sides  of  the  thorax  between 
the  segments,  but  probably  belonging  to  the  mesothorax  and  the 


116  THE    ANATOMY    OF    THE    HONEY   BEE. 

metathorax  (although  the  first  is  often  regarded  as  prothoracic), 
while  the  other  eight  are  situated  on  the  sides  of  the  first  eight 
abdominal  segments — in  the  bee  on  the  lateral  parts  of  the  terga 
(figs.  32  and  33,  Sp).  The  breathing  apertures  are  usually  pro- 
vided with  a  closing  apparatus  of  some  sort  consisting  of  the  swollen 
lips  of  slitlike  spiracles,  of  a  small  lid,  or  of  a  flexible  and  collapsible 
chitinous  ring,  each  with  special  occlusor  muscles  attached.  In  the 
l>ee  a  chitinous  band  surrounds  the  tracheal  tube  opening  at  each 
spiracle,  a  short  distance  from  the  aperture,  and  has  two  opposite 
loops  projecting  on  the  same  side,  connected  by  a  muscle  whose  con- 
traction approximates  the  two  halves  of  the  band  so  as  to  close  the 
lumen  of  the  trachea.*^  It  is  supposed  that  after  an  inhalation  the 
spiracles  are  closed  momentarily,  so  that  the  first  force  of  the  ex- 
piratory contraction  of  the  abdomen  is  exerted  against  the  air  shut 
in  the  tracheae,  with  the  result  of  driving  it  into  the  extreme  tips 
of  the  latter — the  spiracles  then  opening,  the  rest  of  the  contraction 
is  expended  in  exhalation. 

The  internal  tracheal  system  consists,  among  insects  generally, 
of  a  large  tracheal  trunk  lying  along  each  side  of  the  body,  connected 
by  short  tubes  with  the  spiracles  and  by  transverse  commissures  with 
each  other,  while  they  give  off  segmental  branches  into  the  body 
cavity  which  ramify  minutely  upon  the  organs  and  tissues.  In  the 
tliorax  specially  large  tubes  are  given  off  on  each  side  to  the  legs 
and  to  the  bases  of  the  wings,  while  in  the  head  others  go  to  the 
eyes,  antennas  and  mouth  parts.  The  whole  bod}^  is  thus  virtually 
a  lung  with  ten  pairs  of  openings  along  the  sides. 

The  tracheal  system  of  the  bee  (figs.  1,  50,  and  51)  is  best  developed 
in  the  abdomen,  where  the  longitudinal  trunks  are  enlarged  into  two 
enormous  lateral  air  sacs  (TraSr),  which  are  of  greatest  diameter  in 
(he  anterior  end  of  the  abdomen.  They  are  segmentally  counected  by 
large  transverse  ventral  commissures  (fig.  51,  TraCom), most  of  which 
are  themselves  distended  into  small  air  sacs.  Dorsally  the  lateral 
sacs  give  off  in  each  segment  a  large  tube  which  divides  into  two  sac- 
culated branches  (figs.  49  and  50,  HtTraSc)  that  enter  the  pericardial 
chamber  and  supply  the  heart  and  ])ericardial  cells  with  trachea*.  In 
the  thorax  a  large  sac  lies  on  each  side  of  the  propodeum  (figs.  1  and 
50,  7),  which  bears  a  short  tube  opening  to  the  first  abdominal 
spiracle  (figs,  21  and  50,  ISp).  Above  these  sacs  is  a  narrow  trans- 
verse median  one  (figs.  1  and  50,  S)  ()ccuj)ying  the  large  cavity  of 
the  turgid  mesoscutellum  (fig.  21,  Svl.^).  In  the  ventral  part  of  the 
thorax  there  is  a  large  median  posterior  sac  (figs.  1,  50,  and  51,  5) 

"For  M  (l('tnil<Hl  description  of  the  spiniclcs  in  the  hoe  jnid  their  occlusor 
iipparatus  see  Djatbclieuko  (15)00). 


THE   RESPIRATORY   SYSTEM. 


117 


.6^=oxmj 


TraSc 


TraCom- 


FiG.    51.— Tracheal   system    of   worker   showing   lateral   and   ventral   parts   as   seen   from 
above,  with  dorsal  sacs  and  trunks  removed  in  both  thorax  and  abdomen. 


118  THE   ANATOMY   OF   THE   HONEY  BEE. 

which  gives  off  trunks  to  the  middle  and  hind  legs  and  a  large  sac 
on  each  side  (fig.  51,  6  and  6)  to  the  ventro-lateral  Avails  of  the  thorax. 
Two  large  strong  tubes  (figs.  1,  50,  and  51,  Tra) — the  only  tracheae 
in  the  bee's  body  well  developed  as  tubes — extend  backward  from  the 
head  through  the  neck  and  prothorax  to  the  first  thoracic  spiracles 
(figs.  50  and  51,  iSp).  Each  of  these  gives  off  a  branch  which  divides 
into  the  trachea  for  the  first  leg  and  into  another  that  connects  with 
the  posterior  ventral  thoracic  sac  (J).  An  anterior  median  thoracic 
sac  (4)  is  connected  with  the  two  large  anterior  tubes  near  where  these 
enter  the  neck.  In  the  head  are  a  number  of  large  sacs  which  are 
situated  above  the  brain  (see  figs.  1,  50,  and  51,  i),  about  the  bases 
of  the  eyes  and  optic  lobes  (see  figs.  1  and  50,  2).  and  above  the  bases 
of  the  mandibles  (see  fig.  1,  3). 

Nearly  all  of  the  trachea^  in  the  bee's  body  are  excessively  delicate 
and  their  walls  mostly  lack  the  spiral  thickening  that  ordinarily  holds 
a  tracheal  tube  open.  They  are  consequently  very  distensible  and, 
when  inflated,  they  show  as  opaque  glistening  white  vessels,  which, 
however,  when  emi)ty,  are  extremely  difficult  or  actually  impossible  to 
see.  The  smaller  branches  are  so  numerous  and  flabby  in  the  thorax 
and  the  legs  (fig.  1,  LTra)  that  they  appear  to  form  everywhere 
meshworks  or  sheets  of  tiny  glistening  air-cavities  imbedded  between 
the  muscle  fibers.  Only  the  large  trunks  in  the  anterior  part  of  the 
thorax  have  the  normal  tracheal  appearance. 

The  body  of  the  bee  is  thus  most  abuiidantly  aerated,  probably 
more  so  than  that  of  any  other  insect.  The  numerous  large  and 
small  sacs  form  great  storehouses  of  air — tanks  containing  reserve 
supplies  of  oxygen.  They  are  not  present  for  the  purpose  of  lighten- 
ing the  weight  of  the  body,  because  inflation  with  air  does  not 
decrease  the  weight  of  any  object  surrounded  by  air. 

The  respiratory  movements  are  limited  to  the  abdomen  in  tlie  bee 
on  account  of  the  solidity  of  the  thorax.  They  vary  a  great  deal 
according  to  the  activity  of  the  individual.  While  sitting  quietly 
at  the  entrance  of  the  hive  or  walking  slowly  about,  bees  usually 
exhibit  almost  no  respiratory  motion,  only  a  very  slight  vibratory 
trembling  of  the  abdomen  being  noticeable.  Others  that  are  Avalk- 
ing  hurriedly  about  lengthen  and  shorten  the  abdomen  very  perce})ti- 
bly,  the  motion  being  specially  pronounced  at  the  tip.  A  bee  that 
has  just  alighted  after  flying  exhibits  still  more  i)r()n()unced  abdomi- 
nal movements,  not  only  a  contraction  and  expansion  but  an  ujv 
and-down  motion  as  well.  AMien  a  bee  is  becoming  as|)hyxiate(l  in 
a  killing  bottle  the  extension  and  contraction  of  the  abdomen  is  most 
pronounced,  although  nuich  slower  than  in  the  ordinary  breathing 
movements. 

The  nniscles  of  the  abdomen  that  ])r()duce  res])iration  have  been 
described  by  Carlet  (1884),  who  distinguishes  seven  diflerent  sets  of 


THE    FAT    BODY    AND   THi:    (ENOCYTES.  119 

them  as  follows:  There  are  two  dorsal  sets:  (1)  The  intermd  dorsdl^ 
going  from  the  anterior  edge  of  one  tergiim  to  the  anterior  edge  of 
the  next  following  tergiini,  and  (2)  the  exfcmal  dorml,  going  from 
the  lateral  edge  of  one  tergnm  to  the  corresponding  edge  of  the  fol- 
lowing tergum.  Both  of  these  are  expiratory,  since  their  contrac;- 
tions  bring  the  t^vo  segments  togelhei".  On  the  sides  are  three  sets: 
(3)  The  external  oblique^  g(>ii»g  from  the  anterior  edge  of  each  tergum 
to  the  side  of  the  corresponding  sternum;  (4)  the  internal  ohliqve^ 
crossing  under  the  last  from  the  anterior  edge  of  each  tergum  to  the 
side  of  the  preceding  sternum.  These  two  sets  are  likewise  expira- 
tory, because  their  contractions  approximate  the  terga  and  sterna. 
The  third  set  of  lateral  muscles  is  (5)  the  transverse^  lyiiig  between 
the  overlapping  surfaces  of  each  tergum  and  its  corresponding 
sternum  and  being,  therefore,  inspiratory,  because  the  contraction 
separates  the  terga  and  sterna.  Finally,  there  are  two  sets  of  ventral 
nniscles:  (G)  The  extetmal  ventrals  and  the  inte^mal  ventrals^  forming 
a  letter  M  between  the  anterior  edge  of  each  sternum  and  the  one 
following,  and  (7)  the  interventral^  situated  betw^een  the  overlap- 
ping surfaces  of  consecutive  sterna  and  causing  their  separation  by 
contraction.     These  last  are  therefore  also  inspiratory. 

It  would  thus  seem  that  the  abdomen  is  much  better  equipped  with 
expiratory  than  with  inspiratory  muscles.  Perhaps  the  expansion 
is  partly  due  to  elasticity,  and  perhaps,  also,  it  is  true  that  the  abdo- 
men contracts  upon  the  full  tracheae  and  air  sacs,  before  the  spiracles 
open  to  allows  exhalation,  in  order  to  drive  the  air  into  the  farthest 
recesses  and  terminal  tubes  of  the  tracheal  system,  which  necessitates 
an  extra  contractive  force. 

IX.   THE  FAT  BODY  AND  THE  (ENOCYTES. 

The  fat  tissue  of  insects  is  not  miscellaneously  distributed  through 
the  tissues,  imbedded  beneath  the  skin  and  packed  between  the 
muscles,  but  is  disposed  in  sheets  and  strands  Avithin  the  body 
cavity,  especially  in  the  abdomen,  or  forms  a  definite  mass,  the 
fat  hocly.  The  fat  cells  are  large  and  extensively  vacuoled  with 
clear  globules  of  fatty  oils.  In  some  insects  the  fat  bodies  have  a 
brilliant  yellow,  golden,  or  orange  color.  Associated  wdth  the  fat 
cells  are  other  much  larger  and  often  gigantic  cells,  called  oenocytes^ 
attaining  the  largest  size  of  all  the  cells  in  the  body  except  the  eggs. 
They  were  first  discovered  in  segmental  clusters  attached  to  the 
tracheae  near  the  spiracles,  but  they  are  now  known  also  to  be  scat- 
tered through  the  depths  of  the  bod}^  cavity,  w^here  they  occur  im- 
bedded especially  between  the  fat  cells.    The  term  "  oenocyte  "  signi- 


120  THE  ANATOMY  OF  THE  HONEY  BEE. 

fies  merely  that  those  cells  first  observed  by  Wielowiejski,  who  gave 
them  this  name,  were  slightly  wine-colored. 

Both  the  fat  cells  and  the  cenocytes  of  the  honey  bee  have  been 
specially  studied  by  Koschevnikov  (1900),  who  gives  the  history  of 
the  fat  body  as  follows :  In  the  larva  it  consists  of  gigantic  lobes,  the 
cells  of  which  are  in  general  all  alike  and  so  closely  packed  in  30 
or  more  layers  that,  in  the  younger  stages,  most  of  them  assume 
angular  forms.  Many  of  them  are  binucleate,  and  the  protoplasm 
is  strongly  vacuolated  except  for  a  small  area  about  the  nuclei.  In 
the  full-grown  larvae  the  fat  cells  become  globular  and  filled  with  a 
number  of  round  granules,  which,  during  the  early  part  of  the  pupal 
stage,  are  set  free  by  a  dissolution  of  the  cell  walls  and  float  free  in 
the  body  cavity.  In  pupae  a  little  older,  having  even  but  a  very 
thin  chitinous  covering,  the  adult  fat  bod}^  is  fully  formed,  and  yet 
neither  the  disappearance  of  the  larval  granules  and  nuclei  nor  the 
formation  of  new  adult  fat  cells  is  to  be  observed.  It  seems  that 
the  granules  of  the  larval  fat  cells,  set  free  at  the  beginning  of 
histolj^sis,  are  reassembled  about  the  nuclei  to  form  the  fat  cells  of 
the  adult.  In  the  very  young  imago  the  cells  of  the  fat  body  are 
very  distinct,  and  each  possesses  a  considerable  amount  of  protoplasm, 
with  enormous  A^acuoles  which  press  upon  all  sides  of  the  nucleus. 
In  old  bees  the  vacuolation  is  much  reduced  and  may  even  be  entirely 
lacking,  while  the  cells  become  filled  with  a  solid  granular  plasma. 
Old  workers  examined  in  the  fall  show  the  fat  cells  united  into 
syncytia  or  masses  in  which  the  cell  boundaries  are  lost,  although 
the  nuclei  remain  distinct.  A  queen  does  not  appear  to  form  these 
syncytia  in  old  age. 

The  function  of  the  fat  body  is  still  unsettled,  but  we  do  not 
know  of  any  reason  why  it  should  not  be  comparable  physiologically 
with  the  fat  of  vertebrate  animals  and  constitute  a  reserve  supply 
of  materials  which  can  be  used  both  as  food  and  as  a  source  of  heat 
oxidation.  It  has  already  been  stated  (p.  115)  that  insects  main- 
tain several  degrees  of  bod}^  temperature.  Some  entomologists  have 
supposed  that  the  fat  body  gives  rise  to  the  corpuscles  of  the  blood, 
others  have  believed  it  to  be  an  excretory  organ  because  concretions 
of  uric-acid  salts  are  often  found  associated  with  its  cells,  while 
still  others  have  regarded  it  as  the  seat  of  the  combustion  of  waste 
products  by  the  tracheal  oxygen. 

The  oenocytes  of  the  bee  are  described  by  Koschevnikov  (1900)  as 
enormous  cells  imbedded  in  the  fat  bodies.  He  says  that  those  of 
the  larva  persist  into  the  pupal  stage  where  they  undergo  dissolu- 
tion and  disappear,  while  new  imaginal  (enocytes  are  formed  from 
proliferations  of  the  ectodcnnul  epitheliuiu.    The  new  ones  are  at 


THE   FAT   BODY   AND   THE    (ENOCYTES.  121 

first  small  and  increase  about  live  times  in  diameter  hefoie  reaching 
their  adult  proportions.  The  fat  cells  and  the  a'nocytes,  ah  hough 
closely  associated  with  each  otlier,  are  easily  distin<ruishabh»  hy  their 
size  and  by  their  reaction  in  life  to  staining  solutions.  Koschevnikov 
fed  some  bees  honey  or  sugar  siruj)  containing  ses(juichh)rate  of  iron 
and  then,  after  a  few  hours,  removed  the  fat  body,  washed  it  in  ferro- 
cyanide  of  potassium,  and  placed  it  in  alcohol  aci(hdated  with  hydro- 
chloric acid.  He  found  a  precipitate  of  Berlin  bhie  in  the  fat  cells 
while  the  oenocytes  remained  perfectly  colorless.  Thus  he  sliowed 
conclusively  that  the  two  classes  of  cells  are  physiologically  different 
in  life,  although,  he  says,  if  a  piece  of  dissected  fat  body  be  placed 
in  the  staining  solution  the  color  diffuses  alike  throughout  all  the 
cells. 

The  oenocytes  have  a  golden  brown  pigmentation  but  no  differen- 
tiated contents  in  young  workers  and  queens.  In  old  workers,  to- 
ward the  end  of  the  summer,  yellow  granules  begin  to  appear  in 
them.  During  w^inter  and  especially  in  early  spring  the  (enocytes 
of  the  workers  contain  a  great  number  of  these  Granules,  but  thev  are 
present  in  greatest  quantity  in  queens  several  years  old,  while  in  the 
latter  the  fat  cells  also  contain  similar  granules.  Although 
Koschevnikov  admits  that  the  chemistry  of  these  granules  is  entirely 
unknown,  he  thinks  that  they  are  undoubtedly  excretory  substances, 
that  the  waste  products  of  metabolism  are  first  taken  up  by  the  oeno- 
cytes and  then  delivered  to  the  blood,  and  that  the  accumulation  of 
the  granules  in  the  cells  during  old  age  means  the  loss  of  power 
to  discharge  them,  which  brings  on  the  decline  in  the  life  activity  of 
the  bee.  If  this  is  so,  then  the  oenocytes  are,  as  he  states,  excretory 
organs  without  ducts — cells  which  serve  as  depositories  for  waste 
products. 

According  to  this  theory  of  Koschevnikov,  the  oenocytes  might  be 
likened  in  function  to  the  liver  of  vertebrate  animals,  which,  accord- 
ing to  the  present  views  of  physiologists,  is  the  seat  of  the  splitting 
up  of  the  immediate  nitrogenous  products  of  katabolism,  discharged 
into  the  blood  from  the  tissues,  into  those  final  compounds  of  nitro- 
gen excreted  by  the  kidneys. 

\^Tieeler«  also  describes  the  fat  cells  and  oenocytes  of  insects 
as  perfectly  distinct  in  their  origins,  the  fat  cells  arising  from  the 
mesoderm,  w^hich  is  the  embryonic  cell  layer  between  that  which 
forms  the  outer  body  wall  and  that  w^hich  forms  the  embryonic  ali- 
mentary canal,  while  the  oenocytes  are  derived  from  internal  pro- 
liferations of  ectodermal  cells. 

« Concerning  the  Blood  Tissue  of  Insects.  Psyche,  VI,  1892,  pp.  216-220, 
23S-236,  253-258,  PI.  VII. 


122  THE  ANATOMY   OF   THE   HONEY  BEE. 

X.    THE   NERVOUS   SYSTEM   AND   THE   EYES. 

We  have  learned  so  far  that  the  bee  is  a  complex  animal  made  up 
of  a  large  number  of  tissues  and  organs  all  definitely  interrelated,  and 
we  speak  of  these  tissues  and  organs  as  performing  their  own  special 
functions.  Yet,  in  itself,  a  mass  of  cells,  even  though  a  living  mass, 
is  incapable  of  doing  anything — it  is  inert  unless  stimulated  into  ac- 
tion. The  legs  would  not  move,  the  heart  would  not  beat,  the  glands 
would  not  secrete,  the  respiratory  movements  would  not  be  produced, 
and  the  animal  would  cease  to  live  were  it  not  for  a  vital  force  that 
incites  them  all  into  activity.  This  force  is  generated  by  certain 
cells  of  the  nervous  system  and  is  sent  out  to  the  other  organs  along 
the  nerve  cords,  but  we  know  nothing  more  about  it  than  simply  that 
it  exists  in  living  animals  and  is  dependent  upon  the  maintenance  of 
the  nerve  cells. 

Now,  in  order  that  an  animal  may  be  "  alive,"  it  is  not  only  neces- 
sary that  the  muscles  should  be  made  to  contract,  the  glands  to  secrete, 
and  all  the  other  organs  induced  to  perform  their  individual  roles, 
but  it  is  equally  important  that  they  should  all  work  together  and 
accomplish  definite  results.  The  muscles  must  perform  harmonious 
movements  to  produce  walking,  flying,  breathing,  or  swallowing,  the 
heart  must  beat  in  proper  rhythm,  the  glands  must  secrete  their  juices 
at  the  right  time  and  in  needed  amounts.  Hence,  the  functions  both 
of  sfimulatiou  and  coordination  devolve  upon  the  nervous  system. 
The  nerve-cells  generate  a  force  which,  delivered  through  the  nerve- 
fibers  to  the  various  organs,  irritates  the  tissues  into  activity,  but,  at 
the  same  time,  the  cells  send  out  this  force  in  such  a  methodical  man- 
ner that  the  activities  produced  in  the  different  organs  are  definitely 
correlated  and  cooperate  in  maintaining  the  necessary  condition  for 
the  life  of  the  cells. 

The  nervous  system,  however,  is  more  than  simply  the  source  of 
these  physical  and  chemical  processes  that  constitute  the  visible  i)he- 
nomena  of  life,  for  it  is  also  the  seat  of  all  sense  perceptions  and,  in 
the  higher  animals,  of  consciousness.  We  do  not  know,  however,  that 
insect-s  possess  consciousness — that  they  are  actually  aware  of  their 
own  existence,  and  we  therefore  do  not  know  that  they  have  conscious 
sense  perceptions.  We  do  know  that  they  are  affected  by  external 
objects — by  light,  heat,  taste,  odor,  pressure,  and  perhaps  sound 
acting  upon  specially  sensitized  cells  of  the  ectoderm  called  sense 
organs,  but  we  do  not  know  that  the  reaction  of  the  individual  is 
anything  more  than  the  exhibition  of  a  very  highly  developed  re- 
flex nervous  system.  It  is  most  probable  that  bees  do  all  that  they 
do — make  the  comb,  store  up  honey  and  ])ollen,  feed  the  young,  attend 
to  the  wants  of  the  queen,  and  so  on — without  knowing  why,  and  we 
have  no  evidence  that  they  are  even  conscious  of  the  fact  that  they  do 


THE   NERVOUS   SYSTEM   AND   THE   EYES. 


123 


FiQ.  52. — Nervous  system  of  worker,  dorsal  view. 


124  THE  ANATOMY  OF  THE  HONEY  BEE. 


1 


these  things.  Some  authors  have  tried  to  prove  that  insects  reason, 
but  the  burden  of  proof  is  still  with  them.  We  can  admit  that  in- 
sects may  he  possessed  of  very  slight  conscious  intelligence,  but  we 
can  not  admit  that  any  one  has  ever  proved  it.  Of  course,  a  great 
deal  of  very  interesting  insect  literature  owes  its  readableness  to  the 
fact  that  the  author  endows  his  subjects  with  human  emotions  and 
some  intelligence,  or  makes  it  appear  that  they  consciously  do  things 
from  a  blind  sense  of  obligation.  The  bee  of  literature  is  often  quite 
a  different  creature  from  the  bee  of  science. 

If,  then,  we  are  forced  to  admit  that  we  have  no  proof  of  intelli- 
gence or  of  conscious  sensations  in  insects,  we  have,  on  the  other 
hand,  all  the  more  evidence  of  a  very  high  degree  of  nervous  coordi- 
nation. The  body  of  a  bee  can  be  very  greatly  mutilated  and  the 
creature  will  still  remain  "  alive  "  as  long  as  the  nervous  system  is 
left  intact.  The  segments  can  be  cut  apart  and  each  will  yet  be  able 
to  move  its  appendages  as  long  as  its  nerve  center  is  not  destroyed. 
This  shows  that  there  are  numerous  vigorous  centers  of  nervous 
stimulation,  but  proper  coordination  results  only  when  all  the  parts 
are  together  and  intact. 

The  nervous  system  of  insects  (figs.  1  and  52)  is  comparatively 
simple,  consisting  of  a  series  of  small  nerve  masses  Q^iWedi  ganglia 
{Ong)  lying  along  the  mid- ventral  line  of  the  body,  each  two  con- 
secutive ganglia  being  connected  by  a  pair  of  cords  called  the  coiu- 
missures.  The  ganglia  contain  the  nerve  cells,  which  are  the  source 
of  the  stimuli  sent  out  to  the  other  tissues,  while  they  also  receive  the 
stimuli  from  the  ectoderm-al  sense  organs.  Thus  there  are  incoming 
or  ajferent  stimuli  and  outgoing  or  ejferent  stimuli.  The  commis- 
sures and  the  nerve-trunks  that  branch  to  all  parts  of  the  body  con- 
sist of  fibers  which  are  fine  prolongations  of  the  nerve  cells.  These 
fibers  are  the  electric  wires  that  convey  the  stinnili  to  and  from  the 
nerve  centers  and  are  of  two  kinds,  afferent  and  efferent,  according 
to  the  direction  of  the  stimulus  each  transports. 

In  a  generalized  embryo  we  should  theoretically  find  a  nerve  gan- 
glion developed  from  the  ventral  wall  of  each  segment,  making  seven 
head  ganglia,  three  thoracic,  and  at  least  ten  abdominal  ones.  In 
the  adult,  however,  many  of  these  fuse  with  one  another.  In  the 
head,  for  example,  in  place  of  seven  ganglia  there  are  only  two,  one 
situated  above  the  crsophagus,  called  the  hrain^  and  one  situated 
■below  it  and  called  the  suhmsophageal  gangjio/t.  The  connecting 
cords  are  known  as  the  circummsophageal  conwiissures.  The 
brain  is  composed  of  three  embryonic  ganglia,  and  in  the  adults 
of  many  lower  insects  these  are  still  evident  as  three  well-marked 
cerebral  divisions  or  swellings,  called  the  protocerehrmn^  the  deuto- 
ccrehrum^  and  the  tritoccrehrum.  The  first  carries  the  optic  lohes 
and    innervates   the   compound   and   simi)le   eyes,   the   second    bears 


THE    NERVOUS   SYSTEM    AND    'II  IK    KVKS. 


125 


two  large  antennal  lohes,  from  whicli  arc  <j:iv('n  oil'  (he  anlcnnal 
nerves.  The  third  innervates  the  lower  part  of  the  face  and  the 
labrum,  while  it  gives  oif  also  a  pair  of  nerves  which  unite  in  a  sinall 
swelling,  the  frontal  ganglion,  that  lies  between  the  pharynx  and  the 
front  of  the  head.  A  nerve  runs  posteriorly  from  this  on  the  dorsal 
side  of  the  pharynx  or  a»soi)hagus  to  behind  the  brain,  where  it 
divides  into  several  branches,  some  of  which  bear  small  ganglia  while 
others  extend  backward  on  the  oesophagus  to  the  stomach.  These 
nerves,  originating  in  the  frontal  ganglion,  constitute  the  stomato- 
gastric  system^  sometimes  called  also  the  "  sympathetic  system.'' 


OpL 


AntL 
2Br 


SoeGng  " 


AntNv 


Fig.   53. — Brain  and  subcBsophageal  ganglion  of  worffer   and   their  principal   nerves, 

anterior  view. 

The  suboesophageal  ganglion  consists  of  at  most  four  ganglia  which 
innervate  the  mandibles,  the  hypopharvnx,  the  first  maxill?e,  and  the 
labium  or  second  maxillae.  In  adult  insects  the  body  ganglia  also 
veiy  commonly  fuse  with  one  another  in  varying  combinations,  for 
the  number  present  is  always  less  than  the  number  of  segments,  vary- 
ing from  eleven  to  one. 

The  brain  of  the  bee  (fig.  53,  Br)  is  distinctly  composed  of  two 
parts,  the  protocerebrum  ( iBr),  carrying  the  large  optic  lobes  {OpL)^ 
and  the  deutocerebrum  {2Br),  which  consists  principally  of  the  con- 


126  THE  ANATOMY  OF  THE  HONEY  BEE. 

spiciious  antennal  lobes  (AntL)  that  give  off  the  large  antennal 
nerves  [AntNv).  The  tritocerebrum  is  not  present  as  a  distinct  brain 
division,  and  its  nerves,  the  labral  (LrnXv)  and  the  frontal  (FtCom), 
appear  to  arise  from  the  deutocerebrum  at  the  base  of  the  antennal 
lobes.  The  frontal  ganglion  (FtGng),  formed  at  the  union  of  the 
two  frontal  nerves,  gives  off  a  very  small,  anterior,  median  nerve  and 
a  much  larger,  posterior,  stomatogastric  trunk  (Str/Xr,  represented 
in  the  drawing  as  cut  off  a  short  distance  behind  the  frontal  ganglion) 
which  goes  backward  on  the  dorsal  side  of  the  pharynx  beneath  the 
brain.  Behind  the  latter,  and  just  where  the  pharynx  contracts  to 
the  tubular  oesophagus,  the  stomatogastric  nerve  bears  a  pair  of  small 
ganglia  which  are  connected  by  short  nerves  with  the  brain,  and 
then  it  breaks  up  into  branches  that  go  posteriorly  along  the  oesopha- 
gus but  have  not  been  traced. 

The  circumoesophageal  commissures  are  so  short  in  the  bee  that 
the  subcesophageal  ganglion  appears  to  be  attached  directly  to  the 
lower  ends  of  the  brain,  while  the  oesophagus  appears  to  penetrate 
the  latter  between  the  antennal  lobes.  The  three  principal  pairs  of 
nerves  from  the  lower  ganglion  {JldXr,  MxNv^  and  LhNv)  go  to  the 
mouth  parts. 

A  most  thorough  study  of  the  internal  structure  of  the  brain  of 
the  bee  has  been  made  by  Kenyon  (189G),  to  whose  paper  the  reader 
is  referred  if  interested  in  this  subject.  Kenyon 's  descriptions  have 
never  been  verified,  but  his  work  has  an  appearance  of  thoroughness 
and  carefulness.  He  applies  the  term  ''  brain  "  to  both  of  the  nerve 
masses  of  the  head,  distinguishing  the  upper  as  the  ''  dorsocerebrum  '' 
and  the  lower  as  the  ''  ventrocerebrum,''  being  led  to  do  this  from 
physiological  considerations,  the  separation  of  the  two  being  merely 
incidental  to  the  passage  of  the  oesophagus. 

In  the  thorax  of  the  bee  (figs.  1  and  52)  there  are  two  large  ganglia 
{iGng  and  2Gng).  The  first  is  prothoracic,  being  situated  above 
the  prosternum,  in  front  of  the  entosternum  (fig.  52,  Fu^)^  and  it 
innervates  the  prothorax  and  the  first  pair  of  legs.  The  second, 
which  is  situated  in  front  of  the  middle  legs  and  is  protected  above 
by  the  arch  of  the  common  entosternum  of  the  mesothorax  and  meta- 
thorax  (fig.  52,  FK2+3).  is  a  combination  of  the  mesothoracic  and 
nu'tathoracic  ganglia  and  the  first  two  abdominal  ganglia.  This 
composite  structure  is  evident  from  the  fact  that  it  innervates  both 
the  middle  and  the  hind  legs,  the  bases  of  both  pairs  of  wings,  the 
mesothorax,  the  metathorax,  the  pro})odeum,  and  the  first  abdominal 
segment  behind  the  constriction  (the  true  second  segment).  The  first 
and  second  ganglia  of  the  abdomen  (fig.  52,  3(r7ig  and  iGng)  lie  in 
the  first  two  segments  (//  and  ///)  behind  (he  constriction,  which 
are  the  true  second  and  third  segments.  But  since  the  nerve  trunks 
of  these  ganglia  go,  in  each  case,  to  the  segments  behind  them,  we 


THE    NERVOUS    SYSTEM    AND     I  1 1 K    EVES. 


127 


assume  that  thov  really  belong  to  these  lalter  se<rinents,  (hat  is,  to 
segments  ///  and  IV.  The  next  three  ganglia  (o^rnr/,  O'Onr/,  and 
IGiKj)  lie  in  the  segments  they  innervate  (F,  F/,  and  VII)  and, 
hence,  belong  to  the  fifth,  sixth,  and  seventh  abdominal  segments. 
The  last,  that  is,  the  seventh  ganglion,  supplies  all  of  the  segments 
behind  it  with  nerves  and  is  therefore  [)r()bably  a  compound  of  the 
ganglia  originally  belonging  to  the  seventh,  eighth,  ninth,  and  tenth 
segments. 

In  connection  with  the  nervous  system  it  is  most  convenient  to 
give  a  description  of  the  simple  and  compound  eyes.     The  other 


Cor 


Fk;.  54. — Horizontal  section  of  compound  eye  and  optic  lobe  of  worker  (after  Phillips)  : 
BM,  basement  membrane  ;  Cor,  cornea  ;  /wi,  ^m^,  Jtih,  outer,  middle,  and  inner  fibrillar 
bodies  of  optic  lobe;  inner  ch,  inner  chiasma  ;  Om,  ommatidium  ;  OpL,  optic  lobe;  outer 
ch,  outer  chiasma. 

sense  organs  will  be  found  already  described  along  with  the  parts 
on  which  they  are  located  (see  pp.  3G  and  52).  All  the  sense  organs, 
to  be  sure,  are  of  ectodermal  formation  and  are  only  secondarily 
connected  with  the  nervous  system,  but  the  ej^es  are  so  intimately 
associated  with  the  optic  lobes  of  the  brain  that  their  description 
here  seems  most  appropriate. 

The  compound  eye  of  the  bee  (figs.  9  A,  10,  52,  and  53,  E)  has  been 
specially  studied  by  Phillips  (1905)  and  figures  54  and  55  are  re- 
produced from  his  drawings,  while  the  following  statements  are 
based  on  his  paper:  The  convex  outer  surface  or  cornea  of  the  eye 


128 


THE    ANATOMY    OF    THE    HONEY    BEE. 


presents  a  honeycomb  appearance  under  the  microscope,  and  each 
little  hexagonal  facet  is  the  outer  end  of  an  eye  tube  called  an  omma- 


^  h.e. 


o 


%    D 


0-pC-.r^,W 


ES'^'CC 


"i^A'ttn. 


■'^''\f. 


•~«=^. 


<K\©. 


Fig.  55. — Histological  details  of  compound  eye  of  worker  (after  Phillips)  :  A,  entire 
ommatidlum  (somewhat  diaj^rammatic),  adult  ;  R,  entire  ommatldium,  as  if  dissected 
out,  without  outer  pigment  cells  (diagrammatic),  adult;  (\  section  of  entire  om- 
matidlum, showing  (listril)ution  of  pigment,  adult  ;  D,  cross  s(>ction  just  proximal  to 
lens,  slightly  ohlicpie ;  K,  cross  section  through  extreme  distal  ends  of  retinuhe  and 
proximal  ends  of  cones,  slightly  ohlique ;  F,  cross  section  through  retinuhe,  showing 
relation  of  outer  pigment  cells  in  this  region;  (J,  cross  section  through  retinuljp  in 
region  of  nuclei;  H,  cross  section  through  retinulse  In  region  of  proximal  nucleus;  I, 
cross  section  of  eye,  cutting  l)as(>ment  membrane  parallel  (the  distinctness  of  nerve 
fibers  of  each  ommalidium  is  shown  I  ;  li.M,  l>asemenl  memhran(>  ;  CC,  crystalline  cone; 
CL,  crystalline  lens;  c.-p.v.,  corneal  pigment  cell;  h.r.,  hair-cell;  I.rct.n.,  lower  retinular 
nucleus;  n.f.,  nerve  (ilx-r  ;  \r,  nerve;  o.-p.c.  outer  pigment  cell;  rci ,  retinula;  ret.n., 
'retinular  nucleus;   rhh.  rhabdome. 

tidhdii,  all  of"  which  converge  toward  the  internal  base  of  the  eye, 
since  each  is  vertical  to  the  outer  surface.     Figure  54  is  a  horizontal 


THE    NERVOUS   SYSTEM    AND    TIIK    HYES.  129 

section  through  the  eye  and  the  ()])tic  h)be  of  tlie  brain.  The  omnia- 
tidia  {Om)  are  seen  converging  upon  the  hasement  memhrane  (MM) 
which  is  penetrated  by  the  nerve  fibers  from  the  optic  lobe  (OpL). 
The  outer  ends  of  the  ommatidia  are  transparent,  forming  the 
facets  which  together  (;onstitute  the  cornea  {Cor)  of  the  eye.  The 
nerve  fibers,  by  a  complicated  course  through  the  optic  lobe,  reach 
the  nerve  cells  of  the  brain,  which  are  the  true  seat  of  sight  percep- 
tion, as  of  all  other  sensations,  whether  conscious  or  otherwise. 

The  ommatidia  (Om),  or  eye  tubes,  are  separated  from  one  an- 
other by  cells  containing  a  dark  coloring  matter  and  known  as  the 
pigment  cells.  Each  tube  (fig.  55  A)  consists  of  several  parts,  as  fol- 
lows: First,  on  the  outside,  is  a  clear  six-sided,  prismatic  structure, 
with  convex  outer  and  inner  surfaces,  called  the  crystalline  lens  {CL)^ 
and  which  forms  one  of  the  facets  of  the  cornea.  Beneath  the  lens 
is  a  crystalline  cone  {CC)  having  its  apex  directed  inward  and 
followed  by  a  crystalline  rod  or  rhdbdorrie  {rhh)  which  extends  to 
the  basement  membrane  (BM)  through  the  middle  of  the  omma- 
tidium.  (The  rhabdome  is  represented  black  for  the  sake  of  distinct- 
ness in  figure  55  A;  its  natural  appearance  is  more  as  shown  in  B 
and  C.)  Surrounding  the  rod  is  a  circle  of  eight  or  nine  long  re- 
tinulce  cells  (ret),  each  containing  a  conspicuous  nucleus  (ret.  n) 
above  its  middle  and  continuing  basally  into  an  optic  nerve  fiber  (Nv) 
penetrating  the  basement  membrane.  The  arrangement  of  these 
cells  about  the  rhabdome  is  shown  in  cross  section  at  F  and  G.  The 
inverted  apex  of  the  crystalline  cone  (A,  B,  and  C,  CC)  is  sur- 
rounded by  the  corneal  pigment  cells  (c.-p.  c),  while  the  entire  omma- 
tidium  below  the  lens — the  base  of  the  cone,  the  corneal  pigment 
cells,  and  the  retinulse — is  surrounded  by  the  long  outer  pigment 
cells  (o.-p.  (?.),  forming  a  packing  between  all  the  ommatidia,  as 
shown  in  cross  section  at  E. 

The  entire  compound  eye  is  simply  a  modified  part  of  the  epidermis 
(so-called  "  hypodermis  "  of  insect  histologists)  in  which  the  cuticle 
is  transformed  into  the  lenses  or  cornea,  the  cones,  and  the  rods,  the 
epithelium  into  the  pigment  and  retinulse  cells,  and  the  basement 
membrane  into  the  floor  of  the  eye  perforated  by  the  optic  nerve  fibers. 
According  to  Phillips  the  ommatidia  arise  from  the  ectoderm  of  the 
bee  larva  as  groups  of  epithelial  cells  which  become  arranged  in  the 
form  of  spindles  surrounded  b}^  smaller  cells.  The  cells  of  the 
spindles  become  the  retinulse,  while  the  surrounding  small  cells  become 
the  pigment  cells  and  the  cone  cells.  The  cone  cells  come  to  occupy 
a  position  external  to  the  retinulse  by  an  invagination  of  the  latter, 
and,  through  a  transformation  of  most  of  their  protoplasm  into  a 
crystalline  substance,  they  form  the  crystalline  cone  of  the  eventual 
omm^tidium.  The  approximated  edges  of  the  retinulse  cells  are 
22181— No,  18—10 9 


130  THE  ANATOMY  OF  THE  HONEY  BEE. 

transformed  into  the  crystalline  rod.  The  cornea  is  secreted  by  the 
corneal  pigment  cells,  which  at  first  lie  distal  to  the  cone,  and  possibly 
also  by  the  outer  pigment  cells.  The  nerve  fibers  are  formed  as 
differentiated  parts  of  the  retinulse  which  penetrate  through  the  base- 
ment membrane  (fig.  54,  BM)  and  enter  the  retinular  ganglion  be- 
neath it  at  the  outer  end  of  the  optic  lobe  of  the  brain.  Hence  the 
retinula^  are  simph^  sense  end-organs  of  the  skin  comparable  at  an 
early  stage  of  their  development  with  other  sensory  epidermal  cells, 
and  we  thus  see  how  a  simple  layer  of  epithelium  may  be  transformed 
into  such  an  immensely  complex  organ  as  the  compound  eye. 

There  has  always  been  a  great  deal  of  discussion  as  to  how  insects 
see  by  means  of  the  compound  eyes.  The  weight  of  opinion  now 
favors  the  theory  that  they  see  a  part  of  the  object  or  field  of  vision 
with  each  ommatidium.  But  it  is  most  certain  that,  at  best,  most 
insects  see  very  indistinctly,  and,  in  fact,  it  is  often  questioned 
Avhether  they  really  see  the  shape  of  objects  at  all  or  not.  A  few  of 
them,  however,  such  as  dragonflies,  appear  to  have  a  very  acute 
vision.  In  the  case  of  the  honey  bee  there  is  yet  much  difference  of 
opinion  as  to  whether  the  workers  discover  nectar  by  the  bright  color 
of  the  flowers  (i.  e.,  by  the  sense  of  sight)  or  by  the  sense  of  smell. 
The  sense  of  sight  in  bees  and  in  insects  generally,  however,  may  be 
found  elaborately  discussed  in  many  books  dealing  with  the  senses  of 
insects. 

The  simple  eyes  or  ocelli  (figs.  9  A,  10,  52,  and  53,  0)  are  con- 
vstructed  on  quite  a  different  plan  from  that  of  the  compound  eyes, 
each  consisting  of  a  lenslike  thickening  of  the  cuticle  back  of  which 
the  epithelial  cells  are  specially  elongated,  and  sensitized  by  nerve 
connections.  The  ocelli  of  the  bee,  however,  have  never  been  care- 
fully studied. 

XI.    THE   REPRODUCTIVE  SYSTEM. 

The  reproductive  organs  are  those  that  produce  the  cells  from 
Avhich  new  individuals  are  formed.  All  animals  grow  from  at  least 
one  cell  called  the  egg  and  almost  all  from  a  combination  of  the  egg 
with  another  cell  called  a  fipei^matozoon.  The  uniting  of  these  two 
cells  is  called  the  fertilization  of  the  egg.  In  a  few  animals  the  two 
different  kinds  of  reproductive  cells  are  formed  in  the  same  individ- 
ual, but  in  most  of  them,  including  all  insects,  the  sperm  and  the  eggs 
are  produced  in  different  indivi(hials — the  males  and  the  females. 
In  the  honey  bee  the  males  are  called  drones.,  while  the  females  are 
called  queen,s  or  workers^  according  to  their  functions  in  the  hive. 
The  queens  have  the  egg-producing  organs  or  ovaries  greatly  devel- 
of)ed,  while  these  organs  are  rudimentary  in  the  workers.  The  single 
active  queen  in  each  hive,  therefore,  normally  produces  all  the  eggs 
of  the  colony,  while  the  work  of  rearing  and  providing  for  the  brood 


THE    REPRODUCTIVE    SYSTEM.  131 

falls  to  the  lot  of  the  workers.  Most  other  female  insects  lay  their 
eggs  at  some  place  where  the  young  will  })e  able  to  find  food  when  they 
hatch  out,  and  the  mother  never  in  any  way  feeds  or  [)rotects  her 
offspring;  in  most  cases  she  dies  before  her  brood  emerges  from  the 
eggs.  But  the  w^asps  and  bees  are  different  in  that  nearly  all  of  them 
make  a  nest  of  some  sort  for  the  protection  of  the  young  larva?  when 
they  hatch,  in  which  also  they  store  up  food  for  them  to  eat.  In  many 
species  of  wild  bees  all  the  work  of  constructing  the  nest,  laying  the 
eggs,  and  collecting  and  storing  food  for  the  young  devolves  upon 
the  single  female,  as  it  naturally  should,  since  insects  do  not  ordinarily 
have  servants,  and  the  males  of  most  species  are  utterly  irresponsible 
in  such  matters.  In  some  of  the  higher  wasps,  such  as  the  hornets 
and  yellow  jackets,  however,  the  first  females  that  hatch  out  as  adults 
in  the  spring  help  their  mother  provide  for  a  still  larger  family  by 
increasing  the  size  of  the  house  and  collecting  more  provisions. 
Nature  designed  them  for  this  purpose,  moreover,  by  making  them 
all  sterile,  allowing  them  to  retain  the  maternal  instincts,  but  de- 
priving them  of  organs  capable  of  producing  offspring  of  their  own. 
Thus  there  is  here  a  beginning  of  that  division  of  labor  which  reaches 
its  highest  development  in  the  honey  bee,  where  one  form  of  the  fe- 
male is  specialized  entirely  to  produce  the  young  and  the  other  to 
rear  the  brood,  keep  the  home  in  order,  gather  the  food,  and  ward 
off  enemies.  The  differences  between  the  queens  and  the  workers 
are  supposed  to  result  from  the  different  diet  on  which  larvae  designed 
to  be  queens  are  brought  up,  but  a  more  thorough  investigation  of  the 
food  given  to  the  different  larvae  of  the  brood  is  yet  needed  before 
we  can  decide  on  the  merits  of  this  explanation.  The  work  of  numer- 
ous investigators  seems  to  have  demonstrated  conclusively  that  the 
drone  of  the  honey  bee  is  always  produced  from  an  egg  cell  alone — 
that  is.  from  an  unfertilized  egg — while  the  queens  and  workers  are 
produced  from  fertilized  eggs.  The  production  of  eggs  that  develop 
normally  without  the  addition  of  the  male  element  is  called  partheno- 
genesis. In  a  number  of  insects,  such  as  some  species  of  scales,  a  few 
beetles,  and  some  of  the  gall-forming  Hymenoptera.  there  are  no  males 
known,  although  the  females  are  extremely  abundant.  Such  cases 
are  often  regarded  by  entomologists  as  examples  of  parthenogenesis, 
and,  if  they  are  such,  the  result  of  the  development  of  unfertilized 
eggs  is  here  the  formation  of  females  only.  A  few  other  insects,  such 
as  some  of  the  plant  lice,  produce  eggs  that  develop  without  fertiliza- 
tion into  females  or  into  both  males  and  females,  but  such  cases  nearly 
always  occur  in  a  cycle  of  alternating  generations  in  which,  at  some 
stage,  all  the  eggs  are  fertilized.  As  far  as  is  known  the  production 
of  males  alone  from  parthenogenetic  eggs  is  confined  to  the  order 
Hymenoptera. 


132  THE   ANATOMY   OF   THE   HONEY   BEE. 

1.    THE    MALE   ORGANS. 

The  reproductive  organs  of  the  drone  are  shown  b}^  figure  56  A. 
They  consist  of  the  testes  (Tes),  the  vasa  defei^entia  (VDef),  the 
vesiculce  seminales  (Ves)^  the  accessory  or  mucous  glands  (AcGl), 
the  ductus  ejacidatorius  (EjD).  and  the  peyiis  (Pen). 

The  testes  of  the  bee  (Tes)  are  said  to  be  best  developed  in  the  pupa, 
at  which  stage  they  form  the  spermatozoa.  Each  consists  of  a  hirge 
number  of  small  tubules  opening  into  a  collecting  reservoir  at  the  end 
of  the  vas  deferens.  The  spermatozoa  pass  down  through  the  coiled 
vas  deferens  (VDef)  and  collect  in  the  saclike  enlargement  of  this 
duct,  which  constitutes  the  vesicula  seminalis  (Ves).  In  the  mature 
adult  drone  these  elongate  sacs  are  densely  packed  with  the  active 
spermatozoa,  while  the  testes  that  produced  them  become  rudimentary. 
The  vesiculae  when  freshly  dissected  appear  to  be  alive,  for  they 
bend  and  twist  themselves  about  like  small  worms.  Each  opens  by  a 
short  duct  into  the  base  of  the  accessory  mucous  gland  (AcGl)  of  the 
same  side.  These  organs  have  the  form  of  two  great  sacs  and  are 
filled  with  a  thick,  white,  homogeneous,  finely  granular  liquid,  which  is 
supposed  to  mix  with  the  spermatozoa  as  the  latter  are  discharged. 
The  two  open  at  the  bases  into  the  single  median  ejaculatory  duct 
{KjD)  which  opens  into  the  anterior  end  of  the  penis  {Pea).  This  last 
organ,  shown  in  lateral  view  by  figure  56  E,  is  an  unusually  large 
structure  in  the  bee  and  is  deepl}^  invaginated  into  the  cavity  of  the 
abdomen  from  the  end  of  the  ninth  segment  (D,  Pen)  as  already  de- 
scribed (see  page  73).  While  the  penis  is  simply  an  ectodermal  tube, 
its  walls  present  a  number  of  very  curious  differentiations.  The  upper 
part  is  enlarged  into  a  bulb  (fig.  56  A  and  E,  B  and  PenB)  having 
two  large  irregular  but  symmetrical  chitinous  plates  {tt)  in  its  dorsal 
wall,  beneath  which  is  a  large  gelatinous  thickening  (B,  ss). 
Near  the  base  of  the  bulb  is  a  double  pinnate  lobe  (A  and  E,  uii) 
projecting  from  the  dorsal  wall.  Below  this,  on  the  ventral  side, 
is  a  series  of  close-set,  transverse  plates  (E,  ?v'),  followed  again  by 
hn-gc  dorsal  and  ventral  plates  {wir  and  xx).  The  terminal  part 
makes  a  thin-walled  chamber  (A  and  E,  yy),  from  which  project 
backward  two  very  large  membranous  pouches  {zz)  ending  in  blunt 
]X)ints.  The  whole  tube  of  the  penis  is  capable  of  being  turned 
inside  out,  and  it  is  said  that  copulation  is  effected  by  its  eversion 
into  the  oviduct  of  the  queen,  the  basal  pouches  of  the  penis  {zz) 
being  forced  into  corresponding  pouches  of  the  oviduct,  and  the 
spermatozoa  in  the  bulb  placed  near  the  opening  of  the  sperniatheca 
in  the  vagina.  By  their  own  activity  probably  the  spermatozoa  now 
make  their  way  up  into  this  receptacle  of  the  female,  the  spermatheca, 
where  they  remain  until  ejected  upon  eggs  passing  down  the  oviduct. 
The  spermatozoa  received  from  one  drone  normally  last  the  queen 


THE   REPRODUCTIVE   SYSTEM. 


133 


Pen  AcGl 


VIIS'    YinS    DCS 


Fig.  56. — A,  reproductive  organs  of  drone,  dorsal  view,  natural  position  ;  B,  inner  surface 
of  dorsal  wall  of  bulb  of  penis  (E,  PenB),  showing  gelatinous  thickening  (ss)  ;  C, 
group  of  spermatozoa  and  intermixed  granules  ;  D,  terminal  segments  of  male  abdomen, 
showing  the  seventh  tergum  (VIIT)  removed  from  its  sternum  iVIIS)  and  the  penis 
(Pen)  partly  protruded;  E,  lateral  view  of  penis  as  invaginated  within  abdomen,  and 
ejaculatory  duct   (EjD). 


134  THE  ANATOMY  OF  THE  HONEY  BEE. 

throughout  her  life,  so  that  after  mating  she  goes  into  the  hive  never 
again  to  emerge  except  with  a  swarm,  and  her  entire  life  is  devoted 
to  egg  laying.  The  drone,  on  the  other  hand,  dies  immediately  after 
mating,  while  those  that  do  not  mate  are  driven  out  of  the  hive  in 
the  fall  and  left  to  starve. 

The  spermatozoa  (fig.  56  C)  are  minute  threadlike  cells,  capable  of 
a  vibratory  motion.  As  found  in  the  vesiculae,  they  are  usually  bent 
into  closely  compressed  loops,  although  many  are  extended  to  their 
entire  length.  One  end  is  blunt,  but  not  noticeably  enlarged,  the 
other  is  tapering,  while  the  half  toward  the  tapering  end  seems  to 
be  the  part  chiefly  endowed  with  the  power  of  motion.  The  sperm 
threads  are  contained  in  a  liquid  within  the  vesiculae,  in  which  float 
also  a  great  number  of  minute  granules.  The  vibrations  of  the 
sj^ermatozoa  keep  these  granules  in  constant  motion. 

2.    THE  FEMALE  ORGANS. 

The  organs  of  the  female  that  produce  the  eggs  are  called  the 
ovaries  (fig.  57,  Ov).  In  insects  they  consist  of  a  varying  number  of 
egg  tubules  or  ovarioles  (ov)  forming  two  lateral  groups,  in  each  of 
which  the  tubules  converge  at  both  ends,  the  anterior  ends  being 
drawn  out  into  fine  threads  whose  tips  are  connected,  while  the  poste- 
rior ends  are  widened  and  open  into  the  anterior  end  of  the  oviduct 
(OvD)  on  the  same  side  of  the  body.  An  egg  is  simply  a  very  large 
cell  whose  size  is  due  to  the  great  accumulation  of  yolk  in  its  proto- 
plasm, which  serves  as  food  for  the  future  embryo.  The  eggs  are 
formed  in  the  terminal  threads  of  the  ovarioles  and  are  at  first  appar- 
ently ordinary  undifferentiated  cells,  but  as  they  pass  downward  in 
the  tubule  they  increase  in  size  at  the  expense  of  some  of  the  other 
ovarian  cells.  Hence  the  ovarioles  usually  have  the  form  of  a  string 
of  beads  arranged  in  a  graded  series  from  very  tiny  ones  at  the  upper 
end  to  others  the  size  of  the  mature  egg  at  the  lower  end.  The  two 
oviducts  converge  posteriorly  and  unite  into  the  common  median  duct 
or  vagina  (Vag)  which  in  most  insects  opens  to  the  exterior  upon 
the  eighth  sternum,  as  already  described  in  the  general  account  of  the 
external  anatomy  of  insects  (see  page  25),  but  in  the  bee  and  many 
other  insects  the  eighth  sternum  is  entirely  lacking  as  a  distinct 
sclerite,  and  the  genital  opening  is  therefore  behind  the  seventh  ster- 
num and  below  the  base  of  the  sting.  The  posterior  part  of  the 
vagina  is  very  large,  forming  a  hufs-a  copulatrix  {BCpx).  In  addi- 
tion to  these  parts  there  is  nearly  always  present  in  insects  a  special 
i-eceptacle  for  the  spei'matozoa  called  the  xpcrmatheca  (Spm).  This, 
in  most  insects,  opens  directly  into  the  vagina  as  it  does  in  the  bee,  but 
in  some  it  opens  into  the  roof  of  the  genital  chamber  above  the  eighth 
steriniin.  when  this  is  present,  by  a  se})arate  orifice  behind  that  of  the 


THE   KEPKODUCTIVE   SYSTEM. 


135 


AGID 


Fig.  57.— Reproductive  organs,  sting,  and  poison  glands  of  queen,  dorsal  view. 


136  THE  ANATOMY  OF  THE  HONEY  BEE. 

vagina.  In  the  bee  the  two  poison  glands  {AGl  and  BGl)  do  not 
open  into  the  vagina  but,  as  already  described,  into  the  base  of  the 
sting.  They  are,  hence,  probably  special  organs  having  no  homo- 
logiies  in  nonstinging  insects. 

The  ovaries  of  the  queen  bee  form  two  large  gourd-shaped  masses 
(fig.  57,  Ov)  whose  posterior  or  basal  ends  are  enlarged  and  whose 
anterior  ends  are  narrowed,  curved,  and  attached  to  each  other. 
Since  the  queen  la3^s  eggs  continuously  during  her  entire  life  the 
ovaries  always  contain  eggs  in  all  stages  of  growth,  and  conse- 
quently do  not  vary  so  much  in  appearance  as  they  do  in  those  insects 
that  ripen  only  one  lot  of  eggs  and  deposit  these  all  at  one  time. 

The  structure  of  the  ovarioles  and  the  formation  of  the  eggs  in  the  bee 
have  been  specially  studied  by  Paulcke  (1900)  and  the  following  is 
a  resume  of  his  paper:  The  terminal  threads  of  the  ovarioles  are 
covered  by  a  thin  tunica  propria  and  are  filled  with  a  protoplasmic 
mass  containing  transversely  elongate  nuclei  in  a  single  close  series, 
but  no  cell  outlines.  Farther  down,  in  the  upper  end  of  the  ovariole 
proper,  the  nuclei  become  arranged  in  two  rows,  Avhile  here  also  the 
cell  boundaries  begin  to  appear;  still  farther  along,  where  the  cells 
are  clearly  defined,  the  latter  become  differentiated  into  epithelial 
cells  and  germ  cells.  Next,  the  germ  cells  themselves  divide  into 
^gg  cells  and  food  or  nurse  cells.  When  first  formed  the  Qgg  cells 
occur  in  any  part  of  the  diameter  of  the  tube,  but  they  soon  become 
arranged  in  a  row  down  the  middle  of  the  ovariole  and  are  separated 
by  groups  of  nurse  cells.  The  epithelial  cells  at  this  time  arrange 
themselves  on  the  periphery  just  within  the  tunica  propria,  but 
farther  down  they  form  a  capsule  or  follicle  about  the  Qgg  and,  less 
definitely,  about  the  group  of  nurse  cells  at  its  upper  end.  The  upper 
end  of  the  o^gg  becomes  narrowed  by  a  constriction  of  the  epithelial 
capsule,  w^hich,  however,  does  not  shut  it  off  from  the  nurse  cells, 
a  connection  being  retained  with  the  latter  in  the  form  of  a  neck 
from  the  agg  abutting  against  them.  There  are  48  of  these  nurse 
cells  to  each  egg,  which  fact  is  accounted  for  by  supposing  that  each 
original  germ  cell  divides  into  4,  one  of  which  ceases  further  divi- 
sion and  becomes  the  ^gg  cell,  Avhile  each  of  the  other  3  divides  into 
16  by  four  consecutive  divisions.  The  latter  are  the  nurse  cells  and 
their  function  is  to  nourish  the  e^gg  cells.  They  persist  down  to 
the  time  when  the  i}gg  is  fully  formed,  when  the}^  suddenly  disappear 
by  being  absorbed  bodily  into  its  yolk.  Toward  the  end  of  the 
growth  of  the  agg  the  follicle  cells  become  thinner  and  thinner,  so 
that  when  the  Qgg  is  ready  to  go  into  the  oviduct  it  has  but  a  thin 
meml)rane  to  break  through. 

The  organs  of  most  especial  interest  to  the  student  of  the  bee  are  the 
spermatheca  and  the  apparatus  by  means  of  wliicli  the  queen  is  able 
to  dole  out  the  spermatozoa  to  the  eggs  as  she  deposits  the  latter. 


THE   REPRODUCTIVE   SYSTEM.  137 

The  spermatheca  consists  of  a  glol)iilar  soniinal  sac  (fig.  57,  Spm)^ 
of  a  pair  of  tubular  accessory  glands  (SpmGl).  and  of  a  duct  whose 
upper  end  is  connected  with  the  sac  and  receives  also  the  duct  of  the 
glands,  and  whose  lower  end  opens  into  the  anterior  part  of  the 
dorsal  wall  of  the  vagina  just  caudad  of  the  united  bases  of  th(^ 
oviducts. 

The  spermatozoa  are  discharged  by  the  male  into  the  upjuM-  end 
of  the  vagina,  and  in  some  manner  they  make  their  way  \i\)  into  the 
sperm  sac  through  the  duct.  Cheshire  (1885)  described  the  latter 
as  forking  toward  its  lower  end  into  an  anterior  branch  which  opens 
into  the  vagina  and  into  a  posterior  branch  which  turns  backward 
and  becomes  lost  in  the  lower  end  of  the  vaginal  wall.  This  second 
branch  he  believes  is  open  in  the  young  queen  and  is  the  one  through 
which  the  spermatozoa  enter  the  sac.  Breslau  (1906)  has  shown,  how- 
ever, that  Cheshire  was  entirely  wrong  in  his  supposed  observation 
of  the  forking  of  the  duct,  that  the  latter  is  a  single  tube,  and  that 
consequently  the  spermatozoa  must  both  enter  and  leave  the  sac  by  the 
same  conduit.  It  used  to  be  supposed  that  the  sperm  sac  had  muscular 
walls  and  that  it  forced  the  spermatozoa  out  as  from  a  compressed 
bulb,  but  Breslau  has  shown  that  this  also  is  a  mistaken  notion,  that 
the  walls  of  the  sac  are  entirely  devoid  of  muscular  fibers,  and  that 
the  spermatozoa  are  sucked  out  by  a  muscular  apparatus  in  the  wall  of 
the  duct,  which  structure  he  names  the  sperm  pump.  Cheshire  (1885) 
had  previously  described  this  apparatus  in  a  very  imperfect  manner 
without  recognizing  any  pumping  function,  for  he  supposed  that 
by  the  relaxation  of  certain  muscles  the  spermatozoa  simply  passed  out 
of  the  sac  and  went  down  the  tube.  Breslau  says,  however,  that 
the  spermatozoa  have  not  enough  energ}^  of  their  own  to  come  out  of 
the  sac  and,  hence,  do  not  need  to  be  kept  in  by  a  special  sphincter 
muscle,  as  described  by  Leydig. 

The  upper  end  of  the  sj^ermathecal  duct  makes  an  S-shaped  bend 
just  beyond  the  opening  of  the  sac,  and  a  number  of  muscles  dis- 
posed upon  this  part  constitute  Breslau's  sperm-pump.  Breslau  shows 
that  a  contraction  of  certain  of  these  muscles  flattens  the  bend  of 
the  S  and  causes  an  enlargement  of  the  lumen  of  the  upper  end  of 
the  loop.  This,  therefore,  sucks  into  itself  a  small  bundle  of  sperma- 
tozoa from  the  sac.  The  contraction  then  of  other  muscles  forces 
the  rest  of  the  sperm-threads  back  into  the  mouth  of  the  sac  and 
drives  the  small  bundle  thus  cut  off  down  through  the  duct  and  into 
the  vagina.  Moreover,  Breslau  claims  that  this  explanation  is  not 
theory  only,  for,  by  preparing  histological  sections  from  queens 
killed  at  different  moments  of  egg-laying,  he  procured  specimens 
showing  the  various  stages  in  the  pumping  process  and  in  the  passage 
of  the  sperm  through  the  duct.  Cheshire  calculated  that  a  normal 
queen  lays  1,500,000  eggs  in  her  lifetime  and  that  the  spermatheca 


138  THE  ANATOMY  OF  THE  HONEY  BEE. 

holds  about  4,000,000  spermatozoa,  and  therefore,  allowing  for  drones, 
he  concludes  that  there  can  not  be  more  than  four  sperm-threads  given 
to  each  female  egg.  But  Breslau,  figuring  from  the  size  of  the  sperm- 
bundle  taken  into  the  duct  for  each  egg.  states  that  each  egg  is 
actually  given  75  to  100  spermatozoa.  We  feel  that  the  latter  calcula- 
tion must  be  much  more  reliable  than  that  of  Cheshire  because  it 
is  based  on  an  actual  observation  of  the  size  of  the  sperm  mass  de- 
livered to  the  egg.  Moreover,  the  myriads  and  myriads  of  tiny 
spermatozoa  contained  in  the  spermathecal  sac  make  any  attempt 
at  a  calculation  of  the  number  look  absurd,  and  we  can  not  believe 
that  it  is  possible  to  even  approximate  the  number  present.  Fur- 
thermore, as  Breslau  states,  100  spermatozoa  make  such  an  excessively 
small  bundle  that  it  requires  a  most  effective  and  perfect  apparatus  to 
deliver  even  this  number  with  anything  like  exactness — it  is  incon- 
ceivable that  a  mechanism  could  be  perfect  enough  to  give  out  only 
4  or  5  or  even  7  at  a  time. 

On  the  floor  of  the  vagina,  opposite  the  opening  of  the  spermathecal 
duct,  is  a  free  flap  provided  with  muscles,  which  is  so  situated 
that  when  elevated  its  end  fits  into  the  opening  of  the  duct  above. 
Leuckart  (1858)  explained  this  flap  as  a  contrivance  for  holding  the 
passing  egg  tight  against  the  upper  vaginal  wall  so  that  its  aperture 
through  which  the  spermatozoa  is  received,  called  the  micropyle,  would 
come  against  the  opening  of  the  duct  and  thus  insure  fertilization. 
Breslau,  on  the  other  hand,  does  not  think  the  flap  in  question  has 
any  such  function  and  he  regards  it  as  a  valve  which  by  fitting  into 
the  orifice  of  the  spermathecal  duct  closes  the  latter  and  so  prevents 
the  pump  from  sucking  up  the  contents  of  the  vagina  at  the  same  time 
that  it  sucks  a  bundle  of  spermatozoa  out  of  the  sac.  Since,  howeA^er, 
the  flap  is  on  the  floor  of  the  vagina  and  is  pressed  down  by  the  passing 
egg  it  is  not  clear  how  it  can  at  such  a  time  act  as  a  valve  to  close  the 
orifice  of  the  duct  in  the  dorsal  wall,  since  the  pump  is  supposed  to 
work  by  reflex  action  as  the  egg  is  entering  the  vagina,  though,  of 
course,  it  may  so  function  before  the  egg  has  gone  far  enough  to 
intervene  l)etween  it  and  the  duct  opening;  but  it  would  certainly 
seem  that  a  valve  to  close  the  latter,  if  needed  at  all,  would  be  de- 
veloped in  the  dorsal  wall  of  the  vagina  in  connection  with  the  orifice 
itself.  Furthermore,  a  collapsible  tube  like  the  spermathecal  duct, 
even  though  lined  with  chitin,  should  automatically  close  at  its 
lower  end  when  a  suction  force  is  applied  at  the  upper  end. 

Finally,  Breslau  attributes  to  the  sperm  pump  not  only  the  func- 
tion of  delivering  a  definite  mass  of  spermatozoa  to  each  egg,  but  also 
that  of  sucking  the  spermatozoa  up  from  the  vagina  of  a  newly  fer- 
tilized queen  into  the  spermathecal  sac.  He  does  not  seem  now  to  see 
in  the  valve  any  obstacle  to  such  an  action.  The  spermatozoa  are 
usually  supposed  to  make  their  way  up  the  duct  by  their  own  vibra- 
tory motion. 


EXPLANATION    OF   SYMBOLS   AND   LKTTKItS.  1:^,9 

The  {iimtoniy  of  the  spermatheca  and  the  niuscujhir  apparatus  of  its 
duct  for  delivering  the  spermatozoa  to  the  egg  does  not,  as  Breslau 
points  out,  throAv  any  light  on  the  determination  of  sex  in  bees.  It  is  a 
common  notion  that  all  eggs  of  an  uiirerlilizcd  female  deveh)p  into 
drones,  but  this  is  by  no  means  proved;  in  fact,  there  is  just  as  good 
reason  for  believing  that,  while  no  females  develop,  there  are  also  no 
more  than  the  normal  number  of  drones  produced — the  eggs  that 
might  otherwise  have  developed  into  females,  if  laid  by  a  fertile  queen, 
all  dying  in  the  cells  of  the  comb,  from  which  they  are  removed  by  the 
workers.  Modern  investigation  of  the  determination  of  sex  shows  that 
there  is  probably  just  as  much  reason  in  many  cases  for  supposing  that 
sex  is  established  in  the  egg  of  the  ovary  before  fertilization,  as  there 
is  for  believing  it  to  result  from  fertilization  or  from  subsecpient  en- 
vironment of  the  egg  or  young  embryo.  Hence,  it  is  not  only  very 
doubtful  that  the  queen  determines  the  sex  of  her  offspring  by  con- 
trolling the  fertilization  of  the  eggs,  but  it  is  also  very  uncertain  that 
fertilization  itself  has  anything  to  do  with  it.  Parthenogenesis  in 
the  bee  may  amount  simply  to  this,  that  the  male  eggs,  predetermined 
as  such  in  the  ovary,  are  capable  of  developing  without  fertilization, 
while  the  female  eggs  are  incapable  of  such  a  development  and  die  if 
they  are  not  fertilized. 

Each  unlaid  egg  of  insects  in  general  has  a  small  hole  in  the  upper 
end  of  its  shell,  called  the  micropyle,  which  admits  the  spermatozoa  to 
its  interior.  One  or  several  spermatozoa  may  enter  the  egg  through 
this  aperture,  but  the  nuclear  part  of  only  one  unites  with  the  egg 
nucleus,  this  constituting  the  fertilization  of  the  egg.  After  this  the 
micropyle  closes  and  the  egg  is  deposited  in  a  cell  of  the  comb  by  the 
queen.  The  nucleus  and  a  part  of  the  protoplasm  of  the  egg  then 
begin  to  split  up  into  a  number  of  small  cells  which — but  this  is 
taking  us  into  the  development  of  the  next  generation,  which  is 
beyond  the  limits  of  our  subject,  and  so  here  we  must  stop. 

EXPLANATION    OF    THE    SYMBOLS    AND    LETTERS    USED    ON    THE 

ILLUSTRATIONS. 

The  writer  has  made  an  attempt  to  work  out  a  set  of  convenient 
symbols  for  all  the  principal  external  and  internal  parts  in  the  anat- 
omy of  an  insect.  It  has  been  found,  however,  that  entire  consistency 
is  incompatible  with  practicability,  especially  in  making  compound 
abbreviations,  and,  therefore,  the  latter  has  been  given  first  considera- 
tion in  many  cases.  For  example,  the  symbol  Dct  suggests  the  word 
"  duct "  when  standing  alone  much  better  than  simply  the  letter  D, 
but  such  combinations  as  SaWct  and  OvDct  are  unnecessarily  long 
and  the  shortened  forms  of  SaW  and  OvD  are  sufficiently  suggestive 
of  "  salivary  duct  "  and  "  oviduct."  The  abbreviation  Sc  is  used 
in  such  compound  symbols  as  PsnSc  for  "  poison  sac  "  and  TraSc 


140  THE  ANATOMY  OF  THE  HONEY  BEE. 

for  "'  tracheal  sac.'*  notwithstanding  that  Sc  alone  means  "  subcosta." 
The  symbol  T  is  used  for  "  tergum,"  and  T^,  T ._,  etc.,  and  IT,  I  IT, 
etc.,  indicate  individual  thoracic  and  abdominal  terga,  but  TMcl  is 
used  to  signify  "  transverse  muscle.''  And  so,  in  several  other  cases, 
it  has  been  found  expedient  to  sacrifice  strict  uniformity  to  practical 
considerations. 

A  combination  of  lower-case  letters  duplicating  one  entirely  or 
partly  of  capitals  signifies  that  the  part  so  designated  is  a  part  or  sub- 
division of  the  other.  For  example.  Ten  refers  to  the  principal  part 
of  the  tentorium  and  ten  to  a  minor  part ;  PI  and  pi  are  subdivisions 
of  the  same  pleurum ;  Lmcl  and  Imcl  are  both  longitudinal  muscles. 

The  most  logical  method  of  referring  symbols  to  any  particular 
segment  of  the  body  would  be,  perhaps,  to  prefix  them  with  either  a 
Roman  or  an  Arabic  numeral  corresponding  with  the  number  of  the 
segment.  A  common  objection,  however,  to  both  would  arise  from 
the  fact  that  entomologists  are  not  at  all  agreed  as  to  how  many  seg- 
ments there  are  in  any  region  of  an  insect's  body.  Furthermore, 
Roman  numerals  prefixed  to  all  the  symbols  necessarily  used  on  a 
drawing  of  the  thorax,  for  example,  would  occupy  entirely  too  much 
space.  Finally,  it  is  very  desirable  to  have  a  method  of  referring  to 
repeated  structures  without  implying  any  segmental  connection,  and 
prefixed  Arabic  numerals  are  certainly  most  convenient  and  sug- 
gestive for  such  a  purpose.  A  system  often  adopted  to  indicate  the 
segment  to  which  a  part  belongs,  especially  in  the  thorax,  is  the  use 
of  one,  two,  or  three  accents  in  connection  with  the  abbreviation. 
But  accented  symbols  lack  artistic  unity,  and  some  of  the  accent 
marks  are  too  easily  lost  in  the  engraving  and  printing.  For  these 
several  reasons  the  writer  has  adopted  the  following  system : 

Numerical  order  of  any  repeated  structure  is  indicated  by  an 
Arabic  numeral  placed  before  the  abbreviation,  and  has  no  segmental 
significance.  Thus  IP^  2P^  etc.,  mean  simply  "  first  parapterum," 
"second  parapterum,"  etc;  iGng^  2Gng,  etc.,  mean  "first  ganglion," 
"  second  ganglion,"  etc.,  without  implying  that  the  ganglion  belongs 
to  any  particular  segment. 

Symbols  are  referred  to  the  prothorax,  the  mesothorax,  or  the  meta- 
thorax,  respectively,  by  the  figures  1,  2,  and  3  placed  below  and 
after  them,  except  on  the  wings,  where  sucli  numbers  designate  the 
branches  of  the  veins  according  to  the  Comstock-Xeedham  system. 

The  abdominal  segments,  counting  the  propodeum  as  the  first,  are 
indicated  by  tlie  Roman  numerals  /  to  X,  and,  when  any  one  of  these 
is  placed  l)efore  an  abbreviation,  it  refers  the  symbol  to  that  indi- 
vidual segment. 

The  lower-case  letters  are  used,  singly  and  in  pairs,  to  refer  to 
miscellaneous  parts  having,  in  most  cases,  no  individual  or  general 
anatomical  names. 


EXPLANATION    OF    SYMBOLS    AND    LETTERS. 


141 


L    SYMUOLS. 


A, 

AcGl, 

AGl, 

AGID, 

An, 

ANP, 

ANR, 

Ant, 

AntL, 

AntNv, 

Ao, 

Ap, 

Aph, 

Ax, 


AxC, 
AxM, 


B, 

BG, 

he, 

BCpx, 

BGl, 

BM, 

Br, 

IBr, 

2Br, 

3Br, 

Brb, 

BW, 

C, 

Cb, 

GC, 

Gd, 

Ger, 

GL, 

Gl,   Gls, 

Gla, 

dp, 

Glsp, 

IGlsp, 

2Glsp, 

Gom, 

Gor, 

Gtl, 

Gu, 


anal  vein;  lA,  first  anal,  2A,  second  anal,  etc-. 

accessory  gland  of  male  reprodnctive  organs. 

acid  gland  of  sting,  ((pcning  into  poison  sac   (I'.snSc). 

duct  of  acid  gland  of  sting. 

anus. 

anterior  wing  process  of  notum. 

anterior  marginal  ridge  of  notum. 

antenna. 

antennal  lobe  of  brain. 

antennal  nerve. 

aorta. 

apodenie,  any  internal  chitinons  process  of  body-wall. 

anterior  phragma  of  any  tergnm,  prephragma. 

the  axillaries  or  articular  sclerites  of  the  wing  base,  designated 

individually  as  lAx,  2Ax,  3Ax,  and  4Ax. 
accessory  axillary  sclerites  of  irregular  occurrence  in  connection 

with  the  principal  axillaries  (Ax). 
axillary  cord,  or  ligament-like  thickening  of  posterior  edge  of  basal 

membrane  of  wing,  attached  to  posterior  angle  of  scutellum. 
axillary  membrane,  the  thin  membrane  of  wing  base,  containing 

the  axillary  sclerites  and  forming  in  some  cases  the  lobes  called 

alulae, 
bulb  (bulb  of  penis  or  of  sheath  of  sting). 
body-cavity, 
any  particular  part  of  body  cavity  such  as  that  prolonged  into  the 

mouth  parts,  legs  or  pieces  of  the  sting, 
bursa  copulatrix. 
alkaline   gland   of   sting, 
basement  membrane, 
brain. 

protocerebrum. 
deutocerebrum. 
tritocerebrum. 
barb. 

body-wall. 

costa,   first  vein  of  wing. 

pollen  basket  or  corbiculum  on  hind  tibia  of  worker, 
crystalline   cone   of   compound    eye. 
eardo. 
cercus. 

crystalline  lens  of  compound  eye. 
cell,    cells, 
claw, 
clypeus. 
clasping  lobes  of  ninth  segment  of  male,  perhaps  equivalent  to  the 

four  gonapophyses  of  ninth  segment  of  female, 
upper    or    outer    clasper. 
lower   or    inner   clasper. 

commissure  (of  either  nervous  or  tracheal  system), 
cornea. 

cuticle,  the  chitinous  layer  of  the  "epidermis, 
cubitus,  fifth  vein  of  generalized  wing. 


142 


THE   ANATOMY   OF   THE   HONEY  BEE. 


Cv, 

cross-vein. 

Cx, 

coxa. 

C.iP. 

pleural    coxa  I    process. 

Dct, 

duct. 

DDph, 

dorsal  diaphragm. 

Dph, 

diaphragm. 

DphCIs, 

diaphragm  cells. 

Dphmh, 

membrane  of  diaphragm. 

DphMcl, 

muscle  fibers  of  diaphragm. 

E, 

compound  ej^e. 

EAiK 

apodeme  of  extensor  muscle. 

EjD, 

ejaculatory  duct. 

Em. 

lateral  emargination  of  notum. 

EMcl, 

extensor  muscle. 

Emp, 

empodium. 

Enz, 

digestive  vesicles  formed  by  ventricular  epithelium. 

Ep, 

epicranium. 

Ephy, 

epipharynx. 

Epm, 

epimerum. 

Eps, 

cpisternum. 

Epth, 

epithelium. 

F, 

femur. 

Fl, 

fiagellum. 

For, 

foramen  magnum. 

Ft, 

front. 

Ft  Com. 

frontal  connnissure. 

FtGng, 

frontal  ganglion. 

FtNv, 

frontal  nerve. 

Fu, 

furca  or  median  entosternal  apodeme  of  thoracic  sterna. 

G, 

gonapophysis. 

Ga, 

galea. 

Ge, 

gena. 

Gh 

gland. 

JGl, 

large  pharyngeal  gland  in  anterior  i)art  of  head  of  worker. 

2GI 

salivary  gland  in  posterior  part  of  hj^vid. 

3G1, 

thoracic  salivary  gland. 

JfGL 

small  median  gland  below  pharyngeal  plate  (s). 

Gls, 

glossa. 

Gny, 

ganglion. 

Gu, 

gula. 

H. 

head. 

Hk, 

hooks  on  front  edge  of  hind  wing. 

Hphy, 

hypopharynx. 

Ifr. 

hair. 

h)\ 

surface  disk  of  "  auditory  "  organ  of  antenna,   i^robably  modified 

base  of  sensory  hair. 

IIS, 

honey  stomach. 

Ht, 

heart. 

ht. 

individiiMJ  chamltoi-  of  heart. 

HtCU, 

pericMnllMl  cells. 

HtTraHr, 

pericardial  tracheal  sac. 

Int,' 

iiitinia,  the  chitlnous  lining  of  any  internal  organ. 

IT, 

fci-guiii   of  first   Mbdoniinal    segnient.    tiu'   nndian   sctiincnt.   or  pro- 

podeum,  incorporated  into  thorax. 

EXPLANATION    OF    SYMBOLS   AND   LETTERS. 


143 


L, 

Lb, 

Lhl, 

LbNv, 

LbPlp, 

Lc, 

Let, 

Lg, 

lAJL 

Lin, 

Lm, 

LMcl, 

Unci, 

LmNv, 

Lr, 

LTra, 

Liim, 

M, 

in, 

Mai, 

Mb, 

mb, 

m-cu, 

MD, 

Md, 

JMdGl, 

2MdGl, 

MdNv, 

Mes, 

Met, 

Mi, 

mi, 

7n-m, 

Mps, 

Mt, 

Mth, 

Mx, 

MxPlp, 

MxNv, 

N, 

Nu, 

Nv, 

O, 

Ob, 

Oe, 

CE, 

CECom, 

Om, 

OpL, 


leg. 

labium. 

labellum. 

labial  nerve. 

labial  pali)us. 

lacinia. 

lancet  of  sting,  equivalent  to  first  gonapoj>bysis  (1(1). 

ligula. 

"lubricating"  gland  of  sting  (not  sliowii  in  figures). 

median  lobe  of  lingua  or  liypopbarynx. 

labrum. 

longitudinal  muscles. 

ventral  longitudinal  muscles  of  thorax. 

labral  nerve. 

lorum. 

trachea  of  leg. 

lumen,  the  cavity  of  any  hollow  organ,  wlietlier  the  glossa,  sting, 

alimentary  canal,  or  gland, 
media,  fourth  vein  of  wing.     M^-M^,  tirst  to  fourth  branches  of 

media, 
median  plate  or  plates  of  wing  base. 
Malpighian  tubules, 
intersegmental  membrane, 
membrane. 

medio-cubital  cross-vein, 
disclike  muscle  apodeme. 
mandible. 

outer  saclike  mandibular  gland, 
inner  racemose  mandibular  gland, 
mandibular  nerve, 
mesothorax,   designated  by  figure  2  placed  after  and  below  any 

thoracic  symbol, 
metathorax.   designated  by   figure  3  placed  after  and  below  any 

thoracic  symbol, 
the  chitinous  plates  of  the  neck  collectively,  the  "  microthorax," 

individually  designated  mi. 
cervical  (microthoracic)  sclerites. 
median  cross-vein, 
mouth  parts  or  trophi. 
mentum. 
mouth, 
maxilla. 

maxillary  palpus, 
maxillary  nerve, 
notum. 
nucleus, 
nerve, 
ocellus, 
oblong  plate, 
occiput, 
oesophagus. 

circumoesophageal  commissures, 
ommatidium. 
optic  lobe. 


144 


THE   ANATOMY   OF    THE   HONEY   BEE. 


Ost, 

Ov, 

ov, 

OvD, 

OvO, 

P, 


IP,  2P, 
3P,  JfP, 
PA, 
Pel, 
PD, 

Pd, 

Pen, 

PenB, 

Peps, 

Pge, 

Pgl, 

Pgu, 

Ph, 

Phy, 

PI, 

Pl, 

PU, 

Pig, 

Pip, 

Pmb, 

PMcl, 

PN, 


pn, 


PNP, 
PNR, 
Pph, 


PR, 

rrh, 
I'rhF.s, 

rs, 

Px, 

Psc, 

Pscl, 

/'.v/. 

PmV, 

PfftiSc, 


ostium  or  lateral  aperture  of  heart. 

ovary. 

ovariole,  individual  ovarian  tube. 

oviduct. 

opening  of  vagina  or  median  oviduct. 

paraptera,  small  pleural  plates  below  base  of  wing,  typically  two 

episternal  paraptera  or  preparaptera  (IP  and  2P) before  pleural 

wing  process  {WP),  and  two  epimeral  paraptera  or  postparap- 

tera  {3P  and  ^P)  behind  wing  process, 
episternal  paraptera,  preparaptera. 
epimeral  paraptera,  postparaptera. 
arm  of  pleural  ridge, 
postclypeus. 
muscle  disc  of  episternal  paraptera,  giving  insertion  to  pronator 

muscle   (not  present  in  the  bee), 
peduncle, 
penis. 

bulb  of  penis. 
preei)isternum. 
postgena. 
paraglossa. 
pregula. 
phragma. 
l)harnyx. 
pleurum. 

subdivision  of  pleurum. 
palpifer,  palpus-carrying  lobe  of  maxilla, 
palpiger,  palpus-carrying  lobe  of  labium, 
palpus. 

peritrophic  membrane, 
pronator  muscle, 
postnotum  or  pseudonotum,  the  second  or  postalar  tergal  plate  of 

the  wing-bearing  segments  of  most  insects,  the  "  postscutellum  " 

of  higher  orders, 
small  rod  connecting  postscutellum    (postnotum  PN)    with   upper 

edge  of  epimerum,  probably  a  detached  piece  of  the  former  (see 

figs.  22  and  24). 
posterior  notal  wing  process, 
posterior  marginal  ridge  of  notum. 
posterior  phragma  or  postphragma  of  any  tergum,  carried  by  the 

second  notal  plate  or  postnotum   (PN),  the  "postscutellum"  of 

higher  forms, 
interna]    pleural    ridge,    the    entopleurum,    marked    externally   by 

pleural  suture  (PS). 
])roboscis. 
fossa  of  proboscis, 
pleural  suture,  external  line  separating  episternum  and  epimerum, 

marking  site  of  internal  j)leural  ridge, 
presternum, 
prescutum. 

postscutellum   (postnotum). 
poststernellum. 
poison  canal  of  sting, 
poison  sac  of  sting  into  which  opens  the  acid  gland  (AOl). 


EXPLANATION   OF   SYMBOLS   AND   LETTERS. 


.45 


Pt,  sensory  pit. 

Ptr,  peritreme,  spiracle-bearing  sclerite. 

Pvent,  proventriculiis. 

Pvent  Vlv,     proventricular  tube  or  valve  in  vcntriculus, 

Qdy  quadrate  plate  of  sting. 

R,  radius,  third  vein  of  generalized  wing,     K,-Kr.,  lirst  to  lifth  branches 
of  radius.     Eg,  radial  sector. 

RAp,  apodeme  of  flexor  muscle. 

Rd,  posterior  extension  or  reduplication  of  any  tergal  or  sternal  plate 
overlapping  plate  following  it. 

Red,  rectum,  the  large  intestine  of  insects. 

RGl,  rectal  glands. 

r-m,  radio-medial  cross- vein, 

RMcl,  flexor  muscle  of  mandible  or  wing. 

IRMcl,  dorsal  retractor  muscle  of  ligula. 

2RMcl,  ventral  retractor  muscle  of  ligula. 

jRs,  radial  sector,  or  second  branch  of  radius  at  first  forking. 

8,  sternum. 

Saw,  salivary  duct. 

SalDO,  external  opening  of  salivary  duct. 

Sc,  subcosta,  second  vein  of  generalized  wing. 

Scl,  scutellum. 

Sep,  scape. 

Set,  scutum, 

Sga,  subgalea. 

Sh,  sheath  of  sting,   equivalent  to  the  second  gonapophyses    (2G)    or 
middle  pair  on  ninth  abdominal  segment. 

ShA,  basal  arm  of  sheath  of  sting, 

ShB,  bulb  of  sheath  of  sting  or  ovipositor. 

ShS,  shaft  of  sheath  of  sting. 

SInt,  small  intestine. 

SI,  sternellum. 

Slin,  superlingua,  embryonic  lateral  lobes  of  hypopharynx,  true  append- 
ages of  fifth  head  segment. 

Smt,  submentum, 

SceGng,  suboesophageal  ganglion. 

Sp,  spiracle. 

Spm,  spermatheca. 

SpmGl,  spermathecal  gland. 

St,  stipes, 

StgNv,  stomatogastric  nerve. 

Stn,  sting. 

StnPlp,  palpuslike  appendages  of  the  sting,  equivalent  to  the  third  gona- 
pophyses {3G)  or  the  outer  pair  on  ninth  abdominal  segment, 

T,  tergum. 

IT,  first  abdominal  tergum,  the  propodeum,  incorporated  into  thorax, 

IITy  second  abdominal  tergum. 

Tar,  tarsus, 

Th,  tibia. 

Ten,  large  tentorial  arms  of  head,  the  mesocephalic  pillars. 

ten,  slender  tentorial  arch  over  foramen  magnum. 

TeSy  testes. 

Tg,  tegula. 

22181— No.  18—10 10 


146 


THE   ANATOMY   OF    THE    HONEY   BEE. 


TMcl, 

Tn, 

TnC, 

Tr, 

Tra, 

TraCom, 

TraSc, 

Tri, 

yaff, 

VDef, 

VDph, 

Vent, 

VentVlv, 

Vesy 

Vlv, 

VMch 

VNR, 

Vx, 

TF, 


transverse  muscle. 

trochantin  (not  separated  from  sternum  in  bee). 

coxal  condyle  of  trochantin. 

trochanter. 

trachea. 

transverse  ventral  tracheal  commissures  of  abdomen. 

tracheal  sac. 

triangular  plate  of  sting. 

vagina. 

vas  deferens. 

ventral   diaphragm. 

ventriculus. 

ventricular  fold  or  vake  in  small  intestine. 

vesicula  seminalis. 

valve  of  sting  carried  by  lancet. 

large  vertical  muscles  of  thorax. 

internal,  median  V-shaped  notal  ridge,  the  "  entodorsum." 

vertex. 

wing. 

mesothoracic  wing  nerve. 

meta thoracic  wing  nerve. 

wing  process  of  pleurum. 


2.    ALPHABETICAL  LETTERING. 


a. 


h 

m, 
n, 

Of 

P, 
Q, 
r, 

t, 

u. 


Wf 


clypeal  suture. 

anterior  tentorial  pit,  in  clypeal  suture. 

posterior  tentorial  pit,  in  occiput  beside  foramen  magnum. 

thickened  posterior  edge  of  lateral  wall  of  fossa  of  proboscis. 

process  at  upper  end  of  d  articulating  with  cardo  of  maxilla  and 

forming  maxillary  suspensorium. 
internal  median  keel  of  vertex  in  cranium  of  drone, 
suspensorial  ligaments  of  anterior  end  of  oesophagus, 
pharyngeal  rod. 

convolutions  of  dorsal  blood  vessel, 
anterior  articular  knob  of  mandible, 
ventral  groove  of  glossa. 
ventral  groove  of  maxillary  rod. 
median  plates  of  wing  base, 
basal  hooks  of  glossa. 
median  ventral  plate  of  ligula. 

dorsal  plates  of  anterior  end  of  mentum,  supporting  ligula. 
inner  wall  of  canal  of  glossa. 
chitinouK  rod  of  glossa. 

pharyngeal  plate,  on  anterior  part  of  floor  of  pharynx, 
salivary  pouch  opening  on  dorsal  side  of  base  of  ligula,  receiving 

connnon  duct  of  salivary  glands  (SalD). 
oblique  muscles   inserted   upon   dorsal    side  of  salivary   pouch   of 

ligula. 
transverse  or  V-shaped  suture  on  surface  of  mesouotum  or  metano- 

tum,  formed  by  the  internal  V-shaped  ridge  or  '*  entodorsum  " 

(V\R). 
lateral    lobe   of   pronotum    projecting    posteriorly   over    the    first 

spiracle, 


EXPLANATION    OF   SYMBOLS   AND    LETTERS.  147 

•p,  thoracic   plate   lying  laterad   of  aiitcu-ior   part   of  stcrniiiu,   ofteu 

regarded  as  a  part  of  presternum. 

y*  accessory  sclerite  of  fourth  axillary  {f,Ax)  of  front  wing,  affording 

nisertion  for  slender  muscle  (fig.  28,  cc)  attached  below  to 
common  apodeme  of  mesosternum  and  metasternum. 

^,  coxal  condyles  of  mesothoracic  and  nielallioracic  sterna,  i)rol)al>ly 

really  the  coxal  condyles  of  trochantins  (fig.  4,  Tn(J)  fused  en- 
tirely with  the  sterna  and  episterna  in  each  segment. 

aa,  muscle  arising  from  inner  wall  of  mesothoracic  pleurum  and  in- 

serted upon  outer  end  of  corresponding  scutellum,  probably  ac- 
cessory in  function  to  the  great  vertical  muscles  (fig.  27,  VMcl) 
between  the  mesothoracic  sternum  and  scutum. 

hh,  coxo-axillary  muscle,  extending  from  upper  end  of  coxa  to  third 

parapterum   {3P). 

cc,  muscle   inserted    upon   accessory    sclerite    {y)    of   fourth   axillary 

(//Aa?)  from  common  entosternum  of  mesothorax  and  meta- 
thorax. 

(Id,  notch  of  antenna  cleaner  on  first  tarsal  joint  (ITar)  of  front  leg. 

ee,  spine  of  antenna  cleaner  situated  on  distal  end  of  tibia  (Th). 

ff,  so-called  "  wax  shears  "  or  "  wax  pincers." 

f/g,  transverse  chitinous  baud  of  empodium   (Etnp),  which  compresses 

its  two  lobes  when  not  in  use  and  spread  out  by  muscular  effort. 

hh,  dorsal  plate  supporting  empodium. 

ii,  ventral  plate  supporting  empodium. 

jj,  dorsal  groove  of  lancet  interlocking  with  ventral  ridge  of  sheath  of 

sting. 

kk,  sting  chamber  within  end  of  seventh  abdominal  segment,  lodging 

sting  whose  accessory  plates  are  derived  from  eighth  and  ninth 
segments. 

7?,  reservoir  of  thoracic  salivary  gland. 

mm,  receptacular  chitinous  pouches  on  ventral  side  of  pharyngeal  plate 

(s)  receiving  ducts  of  large  lateral  pharyngeal  glands  of  head 
ilGl). 

nn,  *'  stomach-mouth  "  at  summit  of  proventricular  projection  within 

honey  stomach  (HS). 

00,  pores  on  lancets  (fig.  40  E)  and  shaft  of  sting  sheath  (F)  open- 

ing to  exterior  from  prolongation  of  body-cavity  (&c)  contained 
in  each. 

pp,  gelatinous  layer  secreted  upon  inner  surface  of  ventricular  epi- 

thelium. 

qq,  food  contents  of  alimentary  canal. 

rr,  cells  of  ventricular  epithelium   apparently   forming  the  internal 

gelatinous  layer. 

ss,  cartilaginous   mass  on   inner  surface  of  dorsal  wall  of  bulb  of 

penis   (fig.  56  E,  PetiB). 

tt,  dorsal  plates  of  bulb  of  penis. 

uu,  fimbriated  dorsal  lobes  of  penis  at  base  of  bulb. 

vv,  ventral  scalariform  row  of  plates  on  tube  of  penis. 

WW,  dorsal  basal  plates  of  penis. 

XX,  ventral  basal  plates  of  penis. 

yy,  basal  pouch  of  penis. 

zZf  copulatory  sacs  of  penis. 


148  THE   ANATOMY   OF   THE   HONEY   BEE. 

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Abnhabt,  Ludwig. 

1906.  Anatomie  und  Physiologie  der  Honigbiene,  99  pp.,  4  pis.,  53  figs.    Wien, 

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1894.  Anatomie  du  tube  digestif  des  Hymenopt§res.     Comptes  Rendus  de 

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1886.  Ueber  die  Anatomie  und  die  Functionen  der  Bienenzunge.     Arch.  f. 
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1884.  Sur  le  venin  des  Hymenopteres  et  ses  organes  secreteurs.     Comptes 

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1890.  Memoir  sur  le  venin  et  I'aiguillon  de  I'abeille.     Ann.  des  Sci.  Nat., 

Zool.,  7  ser.,  IX,  pp.  1-17,  pi.  1. 
1890.  Sur  les  organes  secreteurs  et  la  secretion  de  la  cire  chez  I'abeille. 

Comptes  Rendus  de  I'Acad.  des  Sci.  de  Paris,  CX,  pp.  361-363. 
Chesiiirp:,  Frank  R. 

1885.  The  apparatus  for  differentiating  the  sexes  in  bees  and  wasps.     An 

anatomical    investigation    into   the   structure   of   the   recei)taculum 
seminis  and  adjacent  parts.     Journ.  Roy.  Micr.  Soc,  ser.  2,  V,  pp. 
1-15,  Pis.  I,  II. 
188(5.  Bees  and  bee  keeping,  2  vols.,   London.      (Vol.   I   devoted   mostly  to 
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Clerici,  F. 

1875.  L'Ape  sua  anatomin — suoi  memici.     Milan.     [30  colored  plateS  drawn 
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1907.  Some  stages  in  the  spermatogenesis  of  the  honey  bee.     Troc.  Amer. 

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1903.  Ueber    die    wachsbereitenden    ()rj;an(>    der    Iloni^^'hienc     Zool     An/-., 
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1876.  Anatomie  et  physiologie  de  I'abeille.     Mem.  de  la  Soc.  Polonaise  des 
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1906.  Unsere  Bienen.    Die  Anatomie,  pp.  34-112,  Berlin. 
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1881.  The   endocranium   and   maxillary   suspensorium    of   the  bee.     Amer. 
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1888  and  1889.  Ueber  den  Futtersaft  der  Biene.     Zeit.  f.  Physio.  Chemie, 
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1886.  Die    physiologische    Bedeutung    des    Magenmundes    der    Honigbieue. 
Arch.  f.  Anat.  und  Physiol.,  Physiol.  Abth.,  pp.  451-458. 

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1901.  A  scent-producing  organ   in  the  abdomen  of  the  bee.     Gleanings   in 

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mellifica.     Ent.  Mag.  Lond.,  XXXYIII,  pp.  208-211,  1  fig. 

Wolff,  O.  J.  B. 

1875.  Das  Riechorgan  der  Biene.     Nova  Acta  der  Ksl.  Leop.-Carol.  Deut. 

Akad.  der  Naturf.,  XXXYIII,  pp.  1-251,  pis.  I-VIII. 

Zander,  Enoch. 

1S99.  Beitriige  zur   Morphologic   des   StaclielMppa rates   der   Hynicnopteren. 

Zeit.  f.  wiss.  Zool.,  LXYI,  pp.  2SS-333,  pis.  XYIII,  XIX. 
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Hynicnopteren.     Zeit.  f.   wiss.  Zool.,   LXYII,   pp.   461-489,  9  figs,, 

pi.  XXVU. 


INDEX. 


■pagre 

Abdomen,  defined 1  :i- 1 4 

general  structure 24  20 

of  honey  bee 69-71 

muscles 118-119 

wax  glands  and  sting 69-83 

Absorption 104-105 

Accessory  sternal  plate  in  generalized  thorax 21 

Acid  gland  of  sting 79 

Alimentary  canal 90 

and  its  glands 84-106 

Alkaline  gland  of  sting 79 

Anabolism 86 

Anal  veins  of  generalized  wing 22 . 

Hy  menoptera 59 

Andrena,  pharyngeal  glands 92 

Anteclypeus 15 

Antenna  cleaner 66 

Antennae  and  their  sense  organs 32-39 

defined 16 

of  honey  bee 27,  32-33 

sense  organs 36-39 

Antennal  lobes 125 

Anterior  notal  wing  process,  defined 19 

of  mesothorax  of  honey  bee 62 

metathorax  of  honey  bee 56 

Anthophora,  pharyngeal  glands 92 

Anus 78 

Aorta 108-109 

Apodomes 32 

Appendages 12-13 

Assimilation \ 84-87 

Axillaries,  defined 23 

of  front  wing  of  honey  bee 62 

hind  wing  of  honey  bee 62 

Hymenoptera 59-62 

Axillary  cord,  defined 19 

of  generalized  wing ■ 23 

honey  bee 62 

membrane  of  generalized  wing 23 

honey  bee 61 

Basal  ligament  of  wing.     (See  Axillary  cord.) 

Basement  membrane 129 

Blalta,  development  of  head 18 

Blood 107 

Body  wall 14-15 

151 


]52  THE  A^^\TOMy  of  the  honey  bee. 

Page. 

Bomhus.  pharyngeal  glands 92 

Bouton 45 

Brain,  general  description 124 

of  honey  bee 125-126 

Brood  food 92-94 

production  of,    and  summary  of  facts  known  concerning  it 98-101 

Bursa  copulatrix 134 

Carbohydrates 89 

Cardo,  defined 17 

of  honey  bee 45 

Cells  of  body,  defined 84-86 

wing,  defined 23 

Cerci,  defined 24 

Cervicum 13 

Chiasma,  inner 127 

outer 127 

''Chyle" 101 

' '  stomach  " 90 

' '  Chyme  " 101 

Circulation  of  the  blood 107-111 

Circulatory  system 107-111 

Circumoesophageal  commissures,  defined : 124 

in  honey  bee 126 

Clasping  organs,  defined 24 

of  drone 73 

Claws  of  tarsus 22,  68-69 

Clypeal  suture 28 

Clypeus,  defined 15 

of  honey  bee 28 

Cockroach,  Blatta,  development  of  head 18 

Commissures 124 

Compound  eyes 27 

detailed  structure 127-130 

Conocephalus,  o\'ipositor 25 

Corbicula : 66-68 

Cornea 27,127-129 

Corneal  pigment  cells 129 

Costa  of  generalized  wing 22 

Hymenoptera 59 

Coxa,  defined 20,  22 

of  honey  bee 67 

Coxo-axillary  muscle  of  wing  of  honey  bee 66 

Coxosternum 21 

Cranium,  internal  structure 30-32 

Cricket,  Gryllus  pennsylvanicus,  mouth  parts 16-18 

Crop,  defined 90 

of  honey  bee  (honey  stomach) 94-95 

Cross  veins  of  generalized  wing 22-23 

Crystalline  cone 129 

lens 129 

rod 129 

Cubitus  of  generalized  wing 22 

Hymenoptera 60 


INDEX.  153 

Darts.     (Sec  Lancets.)  Pago. 

Dendroctonus,  ' '  precpisternum  " 20 

Depressor  muscles  of  wing  of  honey  bee f;  1 

Determination  of  sex  in  honey  bees I :'/) 

Deutocerebrum,  defined 121 

in  honey  bee 125-120 

Development,  defined 1112 

Diaphragm  cells 1 10 

Diaphragms,  defined 1 07- J 08 

dorsal 100-1 10 

ventral 109 

Digestion 80,  89 

assimilation,  and  excretion,  general  physiology 84-87 

Dorsal  diaphragm ^ 109-110 

sinus 107-108,  111 

"  Dorsocerebrum  " 126 

Dorsum,  defined 18 

Drones,  defined 130 

Ductus  ejaculatorius 132 

Egg,  defined 130 

fertilization 137, 138, 139 

formation 136 

Elevator  muscles  of  wing  of  honey  bee 64 

Embryo 12-14 

Embryonic  development,  defined 12 

Empodium,  defined 22 

of  honey  bee 68,  69 

Entocranium 31,  32 

Entodorsum,  defined 19 

Entopleurum,  defined 19 

of  mesothorax  of  honey  bee.     {See  Pleural  ridge.) 

Entosternum  (furca),  defined 21 

of  prothorax  of  honey  bee 55 

mesothorax  and  metathorax  of  honey  bee 56 

Entotergum,  defined 19 

Entothorax,  defined 32 

Enzymes 87 

Epicranium,  defined 16 

Epimeral  paraptera  (postparaptera),  defined 20 

of  mesopleurum  of  honey  bee 56 

Epimerum,  defined 19 

of  mesopleurum  of  honey  bee 56 

Epipharynx,  defined 16 

of  honey  bee 51-53 

sense  organs 52-53 

Epipleurites,  defined 24 

Episternal  paraptera  (preparaptera),  defined 20 

of  mesoplem-um  of  honey  bee 56 

Episternum,  defined 19 

of  mesopleurum  of  honey  bee 56 

Excretion 84-87 

Extensor  muscle  of  mandible  of  honey  bee 40 

External  genital  organs  of  drone  honey  bee 72-73 

development 73-74 


154  THE   ANATOMY   OF   THE   HONEY  BEE. 

Page. 

External  mandibular  glands 41 

Eye,  compound 27, 127 

simple 27, 130 

Facets  of  compound  eye 27 

Fat  body 119, 120 

and  oenocytes 119-121 

Female  organs  of  reproduction 134-139 

Femur,  defined 22 

of  honey  bee 67 

Fertilization  of  egg,  defined 130 

of  honey  bee 137-139 

First  abdominal  segment  (propodeum) 58-59 

Flagellum 32-33 

Flexor  muscle  of  mandible  of  honey  bee 40 

wing  of  honey  bee 65 

Food  of  adult  honey  bees 89 

larvae.     {See  Brood  food  and  Royal  jelly.) 

Foramen  magnum,  defined 15 

of  head  of  honey  bee 28 

Fossa  of  proboscis 28, 46 

Frontal  ganglion 125 

Front,  defined 15 

of  head  of  honey  bee 29 

Furca  (entosternum),  defined 21 

of  prothorax  of  honey  bee 55 

mesothorax  and  metathorax  of  honey  bee 56 

Galea,  defined 17 

of  maxilla  of  honey  bee 46 

Ganglia,  defined 124 

' '  Gaumensegel " 52 

Gense,  defined 15 

of  head  of  honey  bee 29 

General  physiology  of  digestion,  assimilation,  and  excretion 84-87 

Gills,  defined 112 

Glands,  external  mandibular 41 

internal  mandibular 42 

lateral  pharyngeal 91,  92 

median  pharyngeal 91 

mucous  glands  of  male  organs 132 

of  Nassanoff 83 

Bting 78-80 

acid 78-79 

alkaline 79 

' '  lubricating  " 78 

postcerebral 87-88 

rectal 90, 106 

salivary,  of  head 87-88 

thorax 88-89 

sublingual 91 

supracerebral 91 

Glossa,  defined 45 

•     details,  in  worker  of  honey  bee 48 

GloHsa*,  defined 17 

of  labium  of  generalized  insect 17,  44 


INDEX.  155 

Page. 

Glossal  rod 48 

Gonapophyses,  defined '2\ 

of  ovipositor  of  loiighomed  grasshopper 25 

sting  of  honey  bee 70 

Grasshopper,  longhorned  ( Conocephalits) ,  ovipositor 2-', 

Growth,  defined 1 1 

Gryllus  pennsylvanicus ,  mouth  parts 10-18 

Gular  sclerites,  defined If; 

Head,  defined I  r> 

of  honey  bee  and  its  appendages 2G-53 

external  structure 26-30 

internal  structure 30-32 

worker,  queen  and  drone,  compared 29-30 

Heart,  chambers 108 

general  description 108 

of  honey  bee 109 

Honey  stomach 90,  94-95 

Horntail,  Sirex  flavicornis,  first  abdominal  segment 58 

metapleurum 57 

wing  veins 60-62 

Humeral  cross- vein,  defined 22 

Hydrocarbons 89 

Hypopharynx,  confusion  with  glossa  of  honey  bee 44 

defined 16, 17 

Hypopleurites,  defined 24 

Hypopygium,  defined 73 

Imago,  defined 12 

Ingluvies,  defined 90 

Insects,  general  external  structure 10-26 

Internal  mandibular  glands 42 

Intersegmental  membrane,  defined 14 

in  abdomen  of  honey  bee 70-7 1 

Intestine 90, 105, 106 

Itycorsia  discolor,  wing  veins 59-61 

Joyful  hum 83 

Katabolism 86 

Labella 45 

Labial  palpi,  defined 17 

of  honey  bee 44 

Labium,  defined 16 

of  generalized  insect ' 17 

honey  bee 27, 44 

Labrum,  defined 15 

of  generalized  insect 16 

head  of  honey  bee 28 

Lacinia,  defined 17 

Lancets  of  sting 75 

Large  intestine 90, 106 

Larva,  defined 12 

Larval  stage,  defined 12 

Lateral  pharyngeal  glands 91-92 

Latus,  defined 18 

Legs  of  generalized  insect 21-22 

worker,  queen,  and  drone 66-69 


156  THE  ANATOMY  OF  THE  HONEY  BEE. 

Page. 

Ligula,  defined 17 

of  honey  bee 44-45 

Lingua,  confusion  with  other  terms 44,  45 

defined 17 

Lorum 46 

"  Lubricating  "  glands  of  sting 78 

Male  organs  of  reproduction 132-134 

Malpighian  tubules,  defined 90 

of  honey  bee 105-106 

Mandibles,  defined 16 

of  generalized  insect 16 

honey  bee 27,  39-41 

Mandibular  glands,  external 41 

internal 42 

Maxillae,  defined 16 

of  generalized  insect 17 

honey  bee 27,  44 

Maxillary  palpus,  defined 17 

of  honey  bee 45 

Maxillary  suspensorium 32 

Median  pharyngeal  glands 91 

plates  of  generalized  wing 23 

segment  (propodeum)  of  Hymenoptera 59 

Media  of  generalized  wing 22 

wings  of  Hymenoptera 60 

Medio-cubital  cross- vein,  defined 23 

Mentum,  defined 17 

of  labium  of  honey  bee 44 

Mesocephalic  pillars 31 

Mesopleurum 56 

Mesosternum 56 

Mesotergum 55 

Mesothorax,  defined 13 

of  honey  bee 55-56 

Metabolism,  defined 86 

process 115 

Metameres,  defined 12 

Metapleurum 57 

Metastemum 56 

Metatergum 56 

Metathorax,  defined 13 

of  honey  bee 56-58 

Micropyle  of  egg,  defined 139 

Microthorax,  defined 13 

of  generalized  insect 18 

Motion  of  wings  in  flight 63 

Mouth,  defined 49 

of  honey  bee ^8 

parts,  defined 16 

of  generalized  insect 16-18 

honey  })oo 27-28,  39-53 

action  in  feeding 46-49 

Mucous  glands  of  male  organs 132 

Muscles  of  flight 63-66 


INDEX.  157 

Neck  or  cervicum,  defined 13 

of  generalized  insect IH 

Nervous  system  and  the  eyes 122-130 

general  description 124-125 

physiology 122-124 

of  abdomen  of  honey  bee 126- 1 27 

head  of  honey  bee 125- 1 20 

thorax  of  honey  bee 120-127 

Notum,  defined •. 19 

Nymph,  defined 12 

Oblong  plate  of  sting 75-76 

Occiput,  defined 15 

of  head  of  honey  bee 29 

Ocelli 27, 130 

(Enocytes 114-115, 120-121 

(Esophagus,  defined 90 

of  honey  bee 94 

Ommatidia  of  compound  eye 128 

Optic  lobes  of  brain 124 

Ostia  of  heart 108 

Ovaries,  defined I34 

structure  in  queen  bee 136 

O varioles,  defined 134 

structure  in  queen  bee 136 

Oviducts,  defined 134 

Ovipositor 24-26 

Palpifer,  defined 18 

of  maxilla  of  honey  bee 45 

Palpiger,  defined 17 

of  labium  of  honey  bee 44 

Palpi,  labial,  defined 17 

of  honey  bee 44 

maxillary,  defined 17 

of  honey  bee 45 

of  sting  of  honey  bee 76 

Paraglossae,  defined 17 

of  labium  of  honey  bee 44, 47 

Paraptera,  defined 20 

of  mesopleurum  of  honey  bee 56 

Parthenogenesis 131 

Penis 132 

Pepsis,  wing  veins 60-62 

Pericardial  air  sacs Ill 

cells Ill 

chamber,  defined 108 

of  honey  bee  (dorsal  sinus) 107,  111 

Peritrophic  membranes 101-102, 104 

Pharyngeal  glands,  lateral 91-92 

median 91 

plate 50, 91 

Pharynx,  defined 90 

of  honey  bee 90-91 

Phragmas,  defined 19 

of  mesotergum  of  honey  bee 55-56 


158  THE  ANATOMY   OF   THE   HONEY   BEE. 

Page. 

Pigment  cells  of  compound  eye 129 

Pleural  coxal  process,  defined 19 

ridge  (entopleurum),  defined 19 

of  mesopleurum  of  honey  bee 56 

suture,  defined 19 

of  mesopleurum  of  honey  bee 56 

wing  process,  defined 19 

of  mesopleurum  of  honey  bee 56 

Pleurites,  defined 14 

Pleurum,  defined H 

of  generalized  insect 19-20 

mesothorax  of  honey  bee 56 

metathorax  of  honey  bee 57 

prothorax  of  honey  bee 55 

Poison  glands  of  sting  of  honey  bee 78-79 

sac  of  sting  of  honey  bee 78-79 

Pollen  baskets  of  worker  bee 66 

Postcerebral  glands 87-88 

Postclypeus,  defined 15 

Postembryonic  development,  defined 12 

Posterior  notal  wing  process,  defined 19 

of  mesothorax  of  honey  bee 62 

metathorax  of  honey  bee 56 

Postgena,  defined 16 

of  head  of  honey  bee 29 

Postnotum  (pseudonotum),  defined 19 

of  mesotergum  of  honey  bee 55-56 

Postparaptera,  defined 20 

of  mesopleurum  of  honey  bee 56 

Postscutellum,  defined 19 

of  mesotergum  of  honey  bee 55 

Poststemellum,  defined 21 

Preepisternum,  defined 19-20 

Preoral  cavity 49 

Preparaptera,  defined 20 

of  mesopleurum  of  honey  bee 56 

Prescutum,  defined 19 

Presternum,  defined 20 

Proboscis 27,  43-51 

Pronator  apparatus  of  wing 65 

Propodeum 58-59 

Proteids 89 

Prothorax,  defined 13 

of  honey  bee 55 

Protocerebrum,  defined 124 

in  honey  bee 125 

Protoplasm 86 

"  Protractor  lingua? " •. 51 

Pro  ventricular  valve 97 

ProveutriculuH,  defined 90 

of  honey  bee 95-98 

Pneudonotum,  defined 19 

I'sifhyrus^  pharyngeal  glands 92 


INDEX.  159 

Pagf. 

Pulvilli,  defined 22 

Pupa,  defined 12 

Pupal  stage,  defined 12 

Quadrate  plate  of  sting  of  honey  bee 76 

Queens,  defined 130 

function  in  hive 130-131 

Radio-medial  cross- vein,  defined 23 

Radius  of  generalized  wing 22 

wings  of  Hymenoptera ! 59-62 

Rectal  glands,  defined 90 

of  honey  bee 106 

Rectum,  defined 90 

of  honey  bee 106 

Reproductive  system 130-139 

of  drone  bee 132-134 

queen  bee 134-139 

Respiration,  movements : 118 

muscles 118-119 

physiology 112-114 

Respiratory  system 112-119 

Retinulae  cells 129 

' '  Retractor  linguse  biceps  " 51 

* '  longus  " 51 

Rhabdomes  of  compound  eye 129 

' '  Riechschleimdriisse  " 41 

Royal  jelly 92-94 

Salivary  glands 87-89 

of  head 87-88 

thorax 88-89 

opening  on  labium 49 

pump 50 

Sawfly,  Itycorsia  discolor,  wing  veins 59-61 

Scape 32 

' '  Schlundbein  " 50 

Sclerites,  defined 14 

Scutellum,  defined 19 

of  mesotergum  of  honey  bee 55 

Scutum,  defined 19 

of  mesotergum  of  honey  bee 55 

Second  maxillae,  defined 17 

Sheath  of  sting 75 

basal  arms 75 

bulb 75 

shaft 75 

Simple  eyes 27, 130 

Sinuses,  defined 107 

Sirez  Jlavicornis,  first  abdominal  segment 58 

metapleurum 57 

wing  veins 60-62 

Small  intestine,  defined 90 

of  honey  bee 105 

Smell,  sense , . , , , , . , , , ,.,.-- 33-39 


160  THE  ANATOMY   OF   THE   HONEY   BEE. 

Page. 

Somites,  defined 12 

Spermatheca,  defined 134-135 

structure  in  queen 136-137 

Spermatozoa,  defined 130 

of  honey  bee 134, 137-138 

Sperm  pump  of  spermatheca 136-138 

Spiracles,  defined 26, 112 

of  honey  bee 115-116 

Sternal  laterale,  defined 21 

Sternellum,  defined 21 

Sternites,  defined 14 

Sternum,  defined 14 

of  generalized  insect 19 

mesothorax  of  honey  bee 56 

metathorax  of  honey  bee 56 

proper,  defined 20 

Stimuli,  afferent,  defined 124 

efferent,  defined 124 

Sting 74-83 

injection  of  poison 80-82 

morphology 77-78 

of  queen  bee 82-83 

Stipes,  defined 17 

of  maxilla  of  honey  bee 45 

Stomach  mouth  (proventriculus) 95-96 

(ventriculus),  defined 90 

of  honey  bee 98 

Stomatogastric  nervous  system,  defined 125 

of  honey  bee 126 

Subcosta  of  generalized  wing 22 

wings  of  Hymenoptera 59 

Subgalea 45 

Sublingual  glands 91 

Submentum,  defined 17 

of  labium  of  honey  bee 44 

Suboesophageal  ganglion,  defined 124 

of  honey  bee 126 

Superlinguae  of  embryo 17 

Supracerebral  glands : 91 

Sutures,  defined 14 

Sympathetic  nervous  system,  defined 125 

of  honey  bee 126 

Tarsus,  defined 22 

of  honey  bee 67 

first  joint 66 

last  joint 68-69 

Taste  organs 52 

Tegula,  defined 23 

Temperature  of  honey  bees 115 

Tenth  segment  of  abdomen 78 

Tentorium 31 

Tergites,  defined 14 


INDEX.  161 

Tergum,  defined II 

in  generalized  thoracic  segment l<j 

of  abdominal  segments  of  honey  bee .  . .  .• (UJ-  70,  72-73 

first  abdominal  segment  of  honey  bee ')S-59 

mesothorax  of  honey  bee 55 

metathorax  of  honey  bee 5(1-57 

prothorax  of  honey  bee 55 

Testes 132 

Thoracic  salivary  glands HH-89 

segment,  typical lH-19 

Thorax,  defined 13 

generalized  segment 18-19 

of  honey  bee  and  its  appendages 53-69 

special  characters,  in  honey  bee 54-55 

Tibia,  defined 22 

of  honey  bee 07 

Tongue 27,  44-45 

Tracheae,  defined 26, 112 

of  honey  bee 116-118 

Triangular  plate  of  sting  of  honey  bee 76 

Tritocerebrum 124 

Trochanter,  defined 22 

of  honey  bee 67 

Trochantin,  defined 20 

of  honey  bee 57-58 

mandibles,  defined 16 

Trophi,  defined 16 

Vagina,  defined 134 

valve 138 

"  Valva  externa  " 73 

' '  interna  " 73 

Yasa  deferentia 132 

Veins  of  generalized  wing 22-24 

^vings  of  Hymenoptera 59-62 

Venter,  defined 18 

Ventral  diaphragm 109 

or  median  pharyngeal  glands 91 

sinus ^. 107-109 

Ventriculus,  defined 90 

of  honey  bee 98 

contents 98 

histology 102-104 

' '  Ventrocerebrum "' 126 

Vertex,  defined 15 

of  head  of  honey  bee 29 

Vesiculse  seminales 132 

Wax  glands 71 

secretion 71-72 

shears 68 

Wing  processes  of  notum,  defined 19 

of  mesonotum  of  honey  bee 62 

metanotum  of  honey  bee 56 

22181— No.  18—10 11 


162  THE   ANATOMY    OF    THE    HONEY   BEE. 

Page. 

^Ying  processes  of  pleura,  defined 19 

of  mesopleurum  of  honey  bee 56 

\Yings,  articulation  in  generalized  insect 23 

honey  bee 62-63 

defined 13 

motion 63 

muscles 63-66 

of  generalized  insect 22-24 

honey  bee 62-66 

Hymenoptera 59-62 

pronator  apparatus 65 

veins 59-62 

Workers,  defined 130 

function  in  hive 130-131 

o 


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